Archived Space Science Seminars

Announcements are sent via the email lists for faculty (SWL-Faculty-L@listserv.gmu.edu) and students (SWL-Students-L@listserv.gmu.edu).  Send an email to one of these lists to subscribe.

Spring 2015

January 14th (Tuesday) 1pm, 242 Planetary Hall

Building the Next-Generation of Model-Based Solar Cycle Predictions

Andrés Muñoz-Jaramillo

Montana State University, Harvard-Smithsonian Center for Astrophysics 

The solar cycle plays a determinant role at shaping the solar magnetic field, defining the conditions of the interplanetary environment, and  driving changes in the Earth’s atmosphere and magnetosphere.  Because of this, solar cycle prediction has become one of the main practical goals of solar physics.  Traditionally, cycle prediction has been performed using the mathematical properties of historical data (extrapolation methods), and/or hunting for observables that correlate with the characteristics of the following cycle (precursor methods).  As a new promising development, the solar minimum of cycle 23 saw the debut of predictions based on the assimilation of solar observations into dynamo models (although with highly varying results).   In this talk we will discuss the relative performance of model-based cycle predictions (compared with other forms of prediction), what caused them to yield such varying results (and what this tell us about the solar dynamo), and some of the steps being taken to improve them.

Tuesday, March 18th at 1pm, 242 Planetary Hall

An Introduction of FORMOSAT-3/COSMIC Occultation Ion Density and Scintillation S4-index Profile

Shih-Ping Chen

The Formosa Satellite 3, also named as the Constellation Observing System for Meteorology, Ionosphere, and Climate (abbreviated as FORMOSAT-3/COSMIC or F3/C in short), is a constellation of six microsatellites, designed to monitor weather via radio occultation observations in both the troposphere and the ionosphere. In this talk, we firstly examine the electron density that F3/C provides thousands of profiles per day since 2006. Secondly, F3/C can also record scintillation S4 index observations between GPS and F3/C satellites (S4max also provided/define), which is calculated from the signal to noise ratio of L1 band C/A code (1.575GHz). With the high spatial and temporal resolutions, especially upon the oceanic region that cannot be provided by ground-based observation, the F3/C data can be used as a powerful investigator of global ionosphere.

Tuesday, April 1st at 1pm, 242 Planetary Hall

The Interaction between Coronal Mass Ejections (CMEs) and Coronal

Holes (CHs) during the Solar Cycle 23 and its Geomagnetic Consequences

Amaal A. Mohamed

Department of Physics, The Catholic University of America, Washington, DC., 20064, USA

Abstract:

The interactions between the two large scale phenomena, coronal holes (CHs) and coronal mass ejections (CMEs) maybe considered as one of the most important relations that having a direct impact not only on space weather but also on the relevant plasma physics. Many observations have shown that throughout their propagation from the Sun to interplanetary space, CMEs interact with the heliospheric structures (e.g., other CMEs, corotating interaction regions (CIRs), helmet streamers, and CHs). Such interactions could enhance the southward magnetic field component, which has important implications for geomagnetic storm generation. These interactions imply also a significant energy and momentum transfer between the interacting systems where magnetic reconnection is taking place. When CHs deflect CMEs away from or towards the Sun-Earth line, the geomagnetic response of the CME is highly affected. Gopalswamy et al. [2009] have addressed the deflection of CMEs due to the existence of CHs that are in close proximity to the eruption regions. They have shown that CHs can act as magnetic barriers that constrain CMEs propagation and can significantly affect their trajectories. Here,we study the interaction between coronal holes (CHs) and coronal mass ejections (CMEs) using a resultant force exerted by all coronal holes present on the disk and is defined as the coronal hole influence parameter (CHIP). The CHIP magnitude for each CH depends on the CH area, the distance between the CH centroid and the eruption region, and the average magnetic field within the CH at the photospheric level. The CHIP direction for each CH points from the CH centroid to the eruption region. We focus on Solar Cycle 23 CMEs originating from the disk center of the Sun (central meridian distance ≤15°). We present an extensive statistical study via compiling data sets of observations of CMEs and their interplanetary counterparts; known as interplanetary CMEs (ICMEs). There are 2 subsets of ICMEs: magnetic cloud (MC) and non-magnetic cloud (non-MC) ICMEs. MCs are identified by a smooth change of the magnetic field as measured with spacecraft at 1 AU, using ACE and Wind spacecraft. It is found that the maximum phase has the largest CHIP value (2.9 G) for non-MCs. The CHIP is the largest (5.8 G) for driverless (DL) shocks, which are shocks at 1 AU with no discernible MC or non-MC. These results suggest that the behavior of non-MCs is similar to that of the DL shocks and different from that of MCs. In other words, the CHs may deflect the CMEs away from the Sun-Earth line and force them to behave like limb CMEs with DL shocks. This finding supports the idea that all CMEs may be flux ropes if viewed from an appropriate vantage point.

Fall 2014

242 Planetary Hall at 1pm

08/26/2014

Wenjing Liang

Regional ionosphere modeling from ground- and space-based GPS data

German Geodetic Research Institute (DGFI)

16/09/2014

Phil Richards

GMU

Causes of high latitude plasma density troughs

09/30/2014

Ron Turner, NASA/HQ

Technology Development in the NASA Innovative Advanced Concepts (NIAC) Program

10/07/2014

Nishu Karna, GMU

Coronal Cavity

10/14/2014

Ray Ladbury, NASA GSFC

How the Sun Knocks Out My Cell Phone from 150 Million Kilometers Away

10/21/2014

Cao Wei Jiang

MHD Simulations of Solar Eruption

10/28/2014

David Siskind, NRL

How weather in the lower atmosphere can drive weather in space

11/04/2014

Weijia Kuang, NASA GSFC

Earth’s magnetic environment: variability, prediction and geophysical implication

11/11/2014

George Chintzoglou, GMU

Sounding rocket experiment to study coronal heating

11/18/2014

Steven Brown, GMU

A study of seasonal ionospheric peak electron density variation

12/01/2014

Alex Kutepov, NASA GSFC/ Catholic U. of America

Breakdown of non-LTE in the planetary atmospheres

12/09/2014

Mel Goldstein, NASA GSFC

The Solar Wind as a Laboratory for the Study of Magnetofluid Turbulence

Spring 2014

Announcements are sent via the email lists for faculty (SWL-Faculty-L@listserv.gmu.edu) and students (SWL-Students-L@listserv.gmu.edu).  Send an email to one of these lists to subscribe.

January 14th (Tuesday) 1pm, 242 Planetary Hall

Building the Next-Generation of Model-Based Solar Cycle Predictions

Andrés Muñoz-Jaramillo

Montana State University, Harvard-Smithsonian Center for Astrophysics 

The solar cycle plays a determinant role at shaping the solar magnetic field, defining the conditions of the interplanetary environment, and  driving changes in the Earth’s atmosphere and magnetosphere.  Because of this, solar cycle prediction has become one of the main practical goals of solar physics.  Traditionally, cycle prediction has been performed using the mathematical properties of historical data (extrapolation methods), and/or hunting for observables that correlate with the characteristics of the following cycle (precursor methods).  As a new promising development, the solar minimum of cycle 23 saw the debut of predictions based on the assimilation of solar observations into dynamo models (although with highly varying results).   In this talk we will discuss the relative performance of model-based cycle predictions (compared with other forms of prediction), what caused them to yield such varying results (and what this tell us about the solar dynamo), and some of the steps being taken to improve them.

Tuesday, March 18th at 1pm, 242 Planetary Hall

An Introduction of FORMOSAT-3/COSMIC Occultation Ion Density and Scintillation S4-index Profile

Shih-Ping Chen

The Formosa Satellite 3, also named as the Constellation Observing System for Meteorology, Ionosphere, and Climate (abbreviated as FORMOSAT-3/COSMIC or F3/C in short), is a constellation of six microsatellites, designed to monitor weather via radio occultation observations in both the troposphere and the ionosphere. In this talk, we firstly examine the electron density that F3/C provides thousands of profiles per day since 2006. Secondly, F3/C can also record scintillation S4 index observations between GPS and F3/C satellites (S4max also provided/define), which is calculated from the signal to noise ratio of L1 band C/A code (1.575GHz). With the high spatial and temporal resolutions, especially upon the oceanic region that cannot be provided by ground-based observation, the F3/C data can be used as a powerful investigator of global ionosphere.

Tuesday, April 1st at 1pm, 242 Planetary Hall

The Interaction between Coronal Mass Ejections (CMEs) and Coronal

Holes (CHs) during the Solar Cycle 23 and its Geomagnetic Consequences

Amaal A. Mohamed

Department of Physics, The Catholic University of America, Washington, DC., 20064, USA

Abstract:

The interactions between the two large scale phenomena, coronal holes (CHs) and coronal mass ejections (CMEs) maybe considered as one of the most important relations that having a direct impact not only on space weather but also on the relevant plasma physics. Many observations have shown that throughout their propagation from the Sun to interplanetary space, CMEs interact with the heliospheric structures (e.g., other CMEs, corotating interaction regions (CIRs), helmet streamers, and CHs). Such interactions could enhance the southward magnetic field component, which has important implications for geomagnetic storm generation. These interactions imply also a significant energy and momentum transfer between the interacting systems where magnetic reconnection is taking place. When CHs deflect CMEs away from or towards the Sun-Earth line, the geomagnetic response of the CME is highly affected. Gopalswamy et al. [2009] have addressed the deflection of CMEs due to the existence of CHs that are in close proximity to the eruption regions. They have shown that CHs can act as magnetic barriers that constrain CMEs propagation and can significantly affect their trajectories. Here,we study the interaction between coronal holes (CHs) and coronal mass ejections (CMEs) using a resultant force exerted by all coronal holes present on the disk and is defined as the coronal hole influence parameter (CHIP). The CHIP magnitude for each CH depends on the CH area, the distance between the CH centroid and the eruption region, and the average magnetic field within the CH at the photospheric level. The CHIP direction for each CH points from the CH centroid to the eruption region. We focus on Solar Cycle 23 CMEs originating from the disk center of the Sun (central meridian distance ≤15°). We present an extensive statistical study via compiling data sets of observations of CMEs and their interplanetary counterparts; known as interplanetary CMEs (ICMEs). There are 2 subsets of ICMEs: magnetic cloud (MC) and non-magnetic cloud (non-MC) ICMEs. MCs are identified by a smooth change of the magnetic field as measured with spacecraft at 1 AU, using ACE and Wind spacecraft. It is found that the maximum phase has the largest CHIP value (2.9 G) for non-MCs. The CHIP is the largest (5.8 G) for driverless (DL) shocks, which are shocks at 1 AU with no discernible MC or non-MC. These results suggest that the behavior of non-MCs is similar to that of the DL shocks and different from that of MCs. In other words, the CHs may deflect the CMEs away from the Sun-Earth line and force them to behave like limb CMEs with DL shocks. This finding supports the idea that all CMEs may be flux ropes if viewed from an appropriate vantage point.

Fall 2013

Meets in Planetary Hall, Room 242 at noon.

Title: Fast Magnetosonic Waves and Global Coronal Seismology in the Extended Solar Corona

Abstract: We present global coronal seismology, for the first time, that allows us to determine inhomogeneous magnetic field strengths in a wide range of the extended solar corona. We use observations of propagating disturbance associated with a coronal mass ejection observed on 2011 August 4 by the COR1 inner coronagraphs on board the STEREO spacecraft. We establish that the disturbance is in fact a fast magnetosonic wave as the upper coronal counterpart of the EIT wave observed by STEREO EUVI. The wave travels across magnetic field lines with inhomogeneous speeds, passing through various coronal regions such as quiet/active corona, coronal holes, and streamers. We derive magnetic field strengths along the azimuthal trajectories of the fronts at heliocentric distances 2.0, 2.5, and 3.0 Rs, using the varying speeds and electron densities. The derived magnetic field strengths are consistent with values determined with a potential field source surface model and reported in previous works. The ranges of the magnetic field strengths at these heliocentric distances are 0.44 ± 0.29, 0.23 ± 0.15, and 0.26 ± 0.14 G, respectively. The uncertainty in determining magnetic field strengths is about 40%. This work demonstrates that observations of fast magnetosonic waves by white-light coronagraphs can provide us with a unique way to diagnose magnetic field strength of an inhomogeneous medium in a wide spatial range of the extended solar corona.

The magnitude and inter-hemispheric asymmetry of equatorial ionization anomaly- CHAMP and GRACE observations

Chao Xiong1, 2, Hermann Lühr1, ShuYing Ma2, Kristian Schlegel3

1. Helmholtz Centre Potsdam, GFZ German Research Centre for Geosciences, Telegrafenberg, 14473 Potsdam, Germany.

2. Department of Space Physics, College of Electronic Information, Wuhan University, 430079 Wuhan, China.

3. Copernicus Gesellschaft e.V., Göttingen, Germany.

 Abstract.

Based on nearly nine years (2001-2009) of observations from CHAMP and GRACE, a comprehensive study has been made on the morphology of the equatorial ionization anomaly (EIA), focusing on the EIA’s magnitude, inter-hemispheric asymmetry by resolving their seasonal and local time variations at different altitudes and solar activity levels. The electron density and the magnetic latitudes of the EIA crests both peak around 1400 LT while the crest-to-trough ratio (CTR) of the EIA reaches its highest value post-sunset around 2000 LT, with a value almost twice the daytime level. The magnetic latitude of the EIA at CHAMP altitude (~400 km) can reach 13° around December solstice during both high and low solar activity years, while at GRACE altitude (~480 km) the crests are observed much closer to the dip equator during low solar activity years. During high solar activity years the averaged apex height of the EIA crests can reach 800 km. During solstice seasons a clear inter-hemispheric asymmetry of the EIA can be seen. At CHAMP altitude the electron density of the EIA crest is stronger in the winter hemisphere during morning to noontime hours. It reverses after the noontime and the transition time appears around 1400 LT and 1200 LT for high and low solar activity years, respectively. At higher altitude (GRACE), the electron density of the EIA crest is always stronger in the summer hemisphere over the whole daytime. Simulation results from the SAMI2 model also show the differences in EIA inter-hemisphere asymmetry at the two altitudes.

Spring 2013

Meets from 12:30-1:30 Research Hall, Room 162.

March 26th

Room moved to Showcase of Research Hall (glass room outside of elevators).

Fall 2012

Meets from 1:30-2:50 Innovation 316.

December 11th

Student presentation. Dan.

November 27th

  • Terry Fu – GPU Computation of MHD Turbulence
  • Phil Richards – AGU presentation

November 13th

Student presentations. Nishu and Andrew.

November 13th

Student presentations. Shea and Phil.

November 6th

John V. Shebalin, NASA Johnson Space Center

Dipole Alignment in Rotating MHD Turbulence

The geodynamo is believed to originate in the highly turbulent liquid outer core of the Earth. There is a strong theoretical similarity between magnetohydrodynamic (MHD) turbulence in a rotating periodic box and that confined by concentric, rotating spherical boundaries. This enables us to use Fourier method numerical simulations as a surrogate for investigating rotating MHD turbulence within the Earth’s liquid core. These simulations indicate strong dipole alignment with the rotation axis as long as there is sufficient time available before the growing dipole locks into a quasistationary coherent structure. Here, results from numerical simulations will be presented, as well as advances in statistical theory that may explain strong dipole alignment observed in simulations, and by extension, help explain alignment seen in planetary magnetic fields.

October 30th

Student presentations.

October 23rd

Jeff Klenzing (GSFC)

The low-latitude ionosphere during the extreme solar minimum

During the recent solar minimum, solar activity reached the lowest levels observed during the space age, resulting in a contracted ionosphere/thermosphere. This extremely low solar activity provides an unprecedented opportunity to understand the variability of the Earthʼs ionosphere. Recent studies of topside ionospheric densities above 400 km as measured by the Communication/Navigation Outage Forecasting System (C/NOFS) satellite show that the plasma density is significantly lower than predicted by empirical models such as IRI-2007. Additionally, the average ExB drifts measured by the VEFI instrument on C/NOFS during this period are found to have several differences from the expected climatology based on previous solar minima, including downward drifts in the early afternoon and a weak to non-existent pre-reversal enhancement. Using SAMI2 as a computational engine, we discuss the effects of a contracted thermosphere, reduced EUV ionization, and altered electrodynamics for this new baseline ionosphere and compare the results to the average ion densities measured by C/NOFS and NmF2/hmF2 measured by COSMIC.

October 16th

Student presentations

October 9th

No class.

October 2nd

No seminar scheduled.

September 25th

No seminar scheduled.

September 18th

Further discussion of SuperDARN Media:SuperDARN-GMU.pdf. Start with student presentations and then follow by discussion.

September 11th

Note: there are two speakers in today’s seminar.

(1) Kyungsuk Cho

KASI (Korea), NASA/GSFC, and CUA

Title: Relationship between Metric Type II Solar Radio Bursts and Coronal Mass Ejections

Metric type II solar radio bursts are known radio signatures of coronal shocks. Since the first discovery of the metric type II burst by Payne-Scott, Yabsley, and Bolton (1947), the debate on the origin (solar flare and/or coronal mass ejection) of the type II bursts has continued. By comparing kinematics of m-type II shocks with those of CMEs observed by SOHO/LASCO C1 & C2, MLSO/MK4, STEREO/COR1, and SDO/AIA, I have investigated the relationship between the type II shocks and CMEs. I found that CMEs could be main source of type II bursts, and suggested that type II bursts are generated in two sites: either at the CME nose or at the CME-streamer interaction site. I will review my studies on the relationship between CMEs and metric type II radio bursts

(2) Roksoon kim

KASI (Korea), NASA/GSFC, and CUA

Title: Magnetic Field Strength in the Upper Solar Corona Using White-light Shock Structures Surrounding Coronal Mass Ejections

To measure the magnetic field strength in the solar corona, we examined 10 fast ( >1000 km/s) limb coronal mass ejections (CMEs) that show clear shock structures in Solar and Heliospheric Observatory/Large Angle and Spectrometric Coronagraph images. By applying the piston–shock relationship to the observed CME’s standoff distance and electron density compression ratio, we estimated the Mach number, Alfven speed, and magnetic field strength in the height range 3–15 solar radii (Rs). The main results from this study are as follows: (1) the standoff distance observed in the solar corona is consistent with those from a magnetohydrodynamic model and near-Earth observations; (2) the Mach number as a shock strength is in the range 1.49–3.43 from the standoff distance ratio, but when we use the density compression ratio, the Mach number is in the range 1.47–1.90, implying that the measured density compression ratio is likely to be underestimated owing to observational limits; (3) the Alfven speed ranges from 259 to 982 km/s and the magnetic field strength is in the range 6–105 mG when the standoff distance is used; (4) if we multiply the density compression ratio by a factor of two, the Alfven speeds and the magnetic field strengths are consistent in both methods; and (5) the magnetic field strengths derived from the shock parameters are similar to those of empirical models and previous estimates.

August 28th

Kile Baker

Title: SuperDARN: What is it, how does it work, and where is it going

Abstract: Incoherent scatter radars (ISR) are well known in the aeronomy community and to some extent in the magnetospheric physics community as well. But coherent scatter radars are much less well known. The first radar that was to become part of the Super Dual Auroral Radar Network (SuperDARN) began operations almost 30 years ago. That original radar has now been joined by 26 others with at least three more in the pipeline. The SuperDARN system is an international consortium that involves universities and research laboratories from 8 countries. The SuperDARN system provides continuous, global measurements of ionospheric convection in both hemispheres. This talk will present a brief review of the history of SuperDARN, a discussion of how the radars work and a look at the future evolution of the radars. Data from the SuperDARN radars are freely available to scientists throughout the world and the data can be used in conjunction with other ground-based data as well as with a large variety of satellite data to study a wide range of geospace phenomena.

Summer 2012

Meets from 1:00-2:00 on Tuesdays in Research Hall room 302.

August 21

Spiros Patsourakos

Departement of Physics, University of Ioannina, Greece

Title: The Nature and Genesis of EUV Waves: A Synthesis of Observations from SOHO, STEREO, SDO, and Hinode

Abstract: A major, albeit serendipitous, discovery of the SOlar and Heliospheric Observatory mission was the observation by the Extreme Ultraviolet Telescope (EIT) of large-scale extreme ultraviolet (EUV) intensity fronts propagating over a significant fraction of the Sun’s surface. These so-called EIT or EUV waves are associated with eruptive phenomena and have been studied intensely. However, their wave nature has been challenged by non-wave (or pseudo-wave) interpretations and the subject remains under debate. A string of recent solar missions has provided a wealth of detailed EUV observations of these waves bringing us closer to resolving the question of their nature. With this talk, we gather the current state-of-the-art knowledge in the field and synthesize it into a picture of an EUV wave driven by the lateral expansion of the CME. This picture can account for both wave and pseudo-wave interpretations of the observations, thus resolving the controversy over the nature of EUV waves to a large degree but not completely. We close with a discussion on several remaining open questions in the field of EUV waves research.

Spring 2012

May 15th

Anand D. Joshi

Udaipur Solar Observatory, Physics Research Laboratory

Title: Kinematics of CMEs and Associated Prominences from Sterescopic Measurements

Abstract: The dynamics of coronal mass ejections (CMEs) and prominences are studied in detail for a long time now. The twin STEREO spacecraft have enabled us to determine the true location and direction propagation of such solar phenomena. In this talk a new triangulation technique that we have developed for the STEREO measurements will be discussed. Based on this technique results from the analysis of two eruptive prominences will be presented. Both the prominences showed pronounced helical twist in their legs during eruption. Several features along the two legs of both the prominence, as observed in the EUVI 304 Angstrom images, were reconstructed. Changes in latitude during the eruptive phase indicate that the prominences underwent a non-radial equator-ward propagation in this phase. True heights of the prominences reveal two phases of eruption: the slow rise and the fast eruptive phase, with constant values of acceleration during both the phases for each reconstructed feature. We have attributed the difference in acceleration of the features along the two legs of the prominences in the fast eruptive phase is because of an interplay between the two motions namely, helical twist and non-radial propagation. Additionally, I would also present a study of six CMEs observed from the COR1 and COR2 coronagraphs. Our study of the kinematics of the CMEs in 3D reveals that the CME leading edge undergoes maximum acceleration typically below 2R_sun. Eruptive prominences associated with three of the CMEs were also analysed. The acceleration profiles of CMEs associated with flares and prominences exhibit different behaviour. Results from this study pertaining to the kinematics of CMEs will also be presented in the talk.

May 1st

Pat Danenault Zhang et al. East-West Coast TEC Differences and then Boding pdf

April 24th

Journal club-style presentation by Phil H. (ajp_746_1_64.pdf) and John R. (“an alternative way to visualize the cross-covariance calculation of Ilonidis” Science-2011-Ilonidis-993-6.pdf).

April 16th

Notice the special time 1:30 PM – 2:30 PM, April 16 (Monday)

Michael Thompson

High Altitude Observatory, the National Center for Atmospheric Research (NCAR)

Helioseismology and the roots of solar activity

Helioseismology provides a unique probe into the structure and dynamics of the solar interior. I will review some of the results from helioseismology that may provide constraints on the generation and evolution of magnetic flux in the solar interior, and I will conclude with a discussion of future challenges.

April 10th

Journal club-style presentation by Nishu and Victoir

April 3rd

John V. Shebalin

NASA JSC

Planetary Dynamos

Many planets in our solar system have global, quasistationary magnetic fields with large dipole moments that interact with the solar wind to create planetary magnetospheres. Strong planetary magnetic fields are believed to arise from magnetohydrodynamic (MHD) processes in a conducting liquid core, although it has taken centuries to reach this viewpoint. In particular, the Earth’s magnetic field has caused wonder and bafflement throughout history, and only in the last century have we come to a more realistic understanding of its origin. I will review past efforts to understand the origins of planetary magnetic fields and also discuss a recent application of ideal MHD theory to “the dynamo problem.”

March 20th

Joseph Helmboldt

NRL

Ionospheric and plasmaspheric science with interferometric VHF data

March 6th

Jeff Stevens will present Meredith et al., Energetic electron precipitation during high‐speed solar wind stream driven storms

February 28th

Dean Pesnell

NASA/GSFC

The Solar Dynamics Observatory: 65 million images of the Sun and 2 comets

NASA’s Solar Dynamics Observatory has returned over 60 million images of the Sun in its first 22 months of taking data. This data has given us spectacular views of flares and erupting prominences. We have learned how to predict when magnetic field will emerge from the surface and why satellite drag caused by solar flares is more complicated then we thought. A comet flew across the face of the Sun on July 6, 2011, causing a bright tail in the images. We are still asking why it was bright. Come hear about the images, see some movies, and learn about the new results from SDO.

February 21st

Pål Breke

Senior adviser at the Norwegian Space Centre in Oslo,

Our Explosive Sun: The Source of the Northern Lights

Our sun is a stormy and variable star that hurls billions of tons of gas toward the Earth, and in the process creates the northern lights, or aurora borealis. This stunning phenomena of lights dancing across the sky is embedded in the mythology of many cultures and has been characterized as everything from dancing spirits to a sign of God’s anger.

Solar physicist Paal Brekke gives a multimedia presentation on the sun-Earth connection, including spectacular images and movies from the new NASA spacecraft Solar Dynamics Observatory as well as mind-bending videos of the northern lights. He also discusses how solar storms can be a hazard for our technology- based society, and for humans in space.

February 14th

Thomas G Moran

GSFC, CUA

Radiative Heating of the Sun’s Corona

The atmosphere surrounding the Sun known as the corona has a temperature of 2,000,000 K, which is a factor of 200 higher than that of the photosphere, or ‘surface’. Therefore, the corona must be heated by a nonconductive mechanism. We consider the possibility that some portion of this heating is provided by sunlight in the visible and infrared and test this idea though a Monte-Carlo simulation of the wave-particle interaction. We conclude that sunlight provides at least 40% and possibly all of the power required to heat the corona, with the exception of dense magnetic flux loops. Coronal electrons are heated in a stochastic manner by low-coherence, solar electromagnetic radiation. The low coherence of solar radiation allows moving electrons to gain energy from the chaotic wave field, which imparts multiple random velocity `kicks’ to these particles causing their velocity distribution to broaden or heat at levels required to balance radiative losses. We propose to test this model through a laboratory experiment, confining electrons in a Penning trap, illuminating them with low coherence broadband visible and infrared light and measuring the resulting heating for comparison with our predictions. This experiment could determine whether sunlight heats the corona.

February 7th

Andrew will lead a discussion of Media:athena_simpleGodunov_2009.pdf

January 31st

Shea will lead a discussion of Media:Science-2011-Ilonidis-993-6.pdf (extra figures Media:Ilonidis-SOM.pdf)

Fall 2011

Meets from 12:00-1:00 on Tuesdays in Research Hall room 301.

November 29

Statistical constraints on outer zone relativistic electron dynamics

T.P. O’Brien

Abstract: Outer zone relativistic electron dynamics are routinely treated as linear in the electron phase-space density. For such linear systems, there is an intimate relationship between the time evolution operator (such as the Fokker-Planck equation) and the spatio-temporal covariance of phase space density. Using particle fluxes observed by the CRRES mission, we exploit this relationship to derive constraints on the time evolution operator. We answer three questions: Is a Fokker-Planck operator appropriate? If so, what diffusion coefficients should be used? What plasma waves must be assumed to obtain the inferred diffusion coefficients?

November 8

Yuan-Yong Deng & Dong-Guang Wang

National Astronomical Observatory, Chinese Academy of Sciences

In this presentation, we will briefly introduce the projects Chinese solar community is proposing, the Space Solar Telescope (SST) and the Chinese Giant Solar Telescope(CGST). SST is a one-meter optical telescope to be launched into L1 to observe the vector magnetic field and line-of-sight velocity. Coordinated with high energy, EUV and radio observation, SST will provide important observation for solar and space weather forecast. CGST is a ground-based solar telescope with an 8m Ring diameter. Its spectral coverage is from visible to mid-infrared region. CGST aims to get high spatial resolution and high magnetic sensitivity, and also wants to get new solar phenomena in the unknown infrared world. As a background, some other progress on solar instrumentation in China will also be summarized in this presentation.

November 1

Laura A. Balmaceda

Institute for Astronomical, Terrestrial and Space Sciences (ICATE), Argentina

Reconstructing Solar Irradiance Variations on Timescales from Decades to Centuries

Solar irradiance variations have been continuously recorded only since 1978. Undoubtedly, there is a need to extend these records into the past in order to evaluate their possible influence on the Earth’s climate. A reconstruction of solar irradiance back to the Maunder minimum from the surface magnetic flux will be described. The reconstruction is based on a simple physical model that builds on the sunspot number records and sunspot areas where available. Since the use of sunspot data from different sources directly combined can lead to errors in estimating the increase of solar irradiance during the past centuries, a description of the cross- calibration of sunspot areas will be also presented. Finally, a brief review on the latest advances in modeling solar irradiance variations on long-term timescales will be discussed.

 

October 18

Dr. Mei Zhang

National Astronomical Observatory, Chinese Academy of Sciences

Consequences of Magnetic Helicity Accumulation in the Corona

Abound observations have shown that magnetic fields emerging on the solar photosphere obey a so-called hemispheric helicity sign rule, that is, positive helicity sign in the southern hemisphere and negative helicity sign in the northern hemisphere. This observational rule, together with the theoretical concept that the total magnetic helicity is approximately conserved in the corona, leads to a natural result that the total magnetic helicity is accumulated in the corona, in respective southern and northern hemisphere. In this talk I will present our understandings on what are the consequences of this magnetic helicity accumulation in the corona. We show that magnetic flux ropes will form in the corona as a result of Taylar relaxation; free magnetic energy will build up according to Woltjer Theorem; coronal mass ejections will take place due to the existence of an upper bound on the total magnetic helicity of force-free fields; and finally Parker-spiral-like structures will form in the interplanetary space to accommodate the large amount of magnetic helicity ejected from the corona.

October 11

Journal papre dicussion led by Phillip Hess

(1)”Propagation of an Earth-Directed Coronal Mass Ejection in Three Dimensions”, Byrne, J. et al, Nature Communications, 1:74 doi:10.1038, 2010

(2) “Experimental Onset Threshold and Magnetic Pressur Pile-up for 3D Reconnection”, Intrator T.P. et al, Nature Physics, 5, 521, 2009

October 04

Dr. Diego Janches

Space Weather Lab, GSFC/NASA

The impact of the micrometeor flux in the Earth’s Mesosphere and Lower Thermosphere

Every day, billions of microgram-sized-extraterrestrial particles enter and ablate in the upper layers of the Earth’s atmosphere, depositing their mass in the Mesosphere/Lower Thermosphere (MLT). These particles, mostly originating from the sporadic meteor complex, are the major contributors of metals in the MLT. The material deposited by these particles gives rise to the upper atmospheric metallic and ion layers observed by radars and lidars. In addition, micrometeoroids are believed to be an important source for condensation nuclei (CN), the existence of which is a prerequisite for the formation of noctilucent clouds (NLC) particles in the polar mesopause region. In order to understand how this flux gives rise to these atmospheric phenomena, accurate knowledge of the global meteoric input function (MIF) is critical. This function accounts for the annual and diurnal variations of meteor rates, global distribution, directionality, and velocity and mass distributions. Estimates of most of these parameters are still under investigation. This talk will focus on results from an effort which aims to address how much, when, where and how micrometeoric mass is deposited in the MLT. This includes radar observations of meteor head-echoes as well as the coupling of several models. These include astronomical, plasma and chemical models interaction and ablation processes that these particles undergo upon atmospheric entry. We then use the Whole Atmosphere Community Circulation Model to study the final distribution of metal through out the MLT.

September 20

Title: Improvements and Applications of Kinematic Models of the Solar Magnetic Cycle

By Andrés Muñoz-Jaramillo (Harvard-Smithsonian Center for Astrophysics)

The best tools we have for understanding the origin of solar magnetic variability are kinematic dynamo models. During the last decade, this type of models has seen a continuous evolution and has become increasingly successful at reproducing solar cycle characteristics. However, the ingredients that are part of these models remain poorly constrained which allows one to obtain solar-like solutions by “tuning” the input parameters, leading to controversy regarding which parameter set is more appropriate. In this presentation we will visit each of those ingredients and the work we have done to constrain their free parameters. Additionally, and using the improved model as a starting point, we will explore the causes that led to the unusually quiet minimum of cycle 23.

September 13

Space Science in the new South African Space Agency

Dr. Lee-Anne McKinnell Managing Director, South African National Space Agency (SANSA) Space Science (formerly NRF Hermanus Magnetic Observatory), Hermanus, South Africa

This presentation will focus on the establishment of the new South African National Space Agency (SANSA) and the role that Space Science will play in the future South African Space programme. Details of the involvement of the agency in Fundamental and Applied research, innovation and technology, space weather, human capital development and science advancement will be covered. The scientific focus on SANSA, with details on the research infrastructure under its care will also be presented.

SANSA Webpage: http://www.sansa.org.za

HMO Webpage: http://www.hmo.ac.za

Space Weather: http://spaceweather.hmo.ac.za

September 6

Title: Investigation of Magnetosheath Cavities and Upper Atmosphere and Space Weather Activities at ITU

By Zerefsan Kaymaz

Istanbul Technical University

In the Earth’s magnetosheath, depressed density and magnetic field regions have been detected during the increased flux of highly energetic particles called Magnetosheath Cavities. Magnetic field and plasma observations from Cluster spacecraft have been scanned to carry out a statistical study on the effects of the energetic particles on the magnetosheath field and plasma structure and to determine the characteristics of the magnetosheath cavities. The magnetosheath cavities are best described as depressions in the magnetosheath magnetic field and density. Temperatures within the cavities are found to be increased while the velocity is seen to be either increased or stays unchanged. As a result of the low density and speed the magnetopause expands locally outward from the Earth.
One of the most distinguishing features that characterize the magnetosheath cavities is the fluctuation levels within the cavity regions in all magnetosheath parameters. Especially in the magnetic field, higher amplitude and higher frequency fluctuations than the background magnetosheath were observed. These indicate wave activity within the cavities. No IMF clock angle relationship has been determined. However, it is found that they occur during the low IMF cone angles (radial IMF). In the results of kinetic-hybrid simulations of the solar wind- magnetosheath interaction under low IMF cone angles, they are seen to be transmitted from the upstream solar wind region into the magnetosheath with the incoming flow. In this talk, results from the Cluster data and kinetic-hybrid simulations will be presented and compared. At the beginning of the talk, a brief introduction on the Upper Atmosphere and Space Weather Laboratory of Istanbul Technical University (ITU) will be given.

Summer 2011

July 26, 2011

11 AM – Noon at Room 302, R1

Title: Can viscous drag account for CME deceleration?

By Prasad Subramanian (IISER Pune, India)

An understanding of the forces that act on Coronal Mass Ejections (CMEs) in the interplanetary medium are of prime importance in understanding their dynamics and predicting their arrival at the Earth. These forces have ben characterized so far in terms of a “drag parameter$C_{\rm D} \sim 1$ that quantifies the role of the aerodynamic drag experienced by a typical CME due to its interaction with the ambient solar wind. We examine this issue critically, and start by examining microphysical models for viscosity in the turbulent solar wind. We envisage the CME as a bubble propagating through the solar wind and compute the drag on it using these viscosity prescriptions applied to a simple 1D hydrodynamical model. We find that the viscous drag is very inadequate to account for the observed slowing down of CME from the Sun to the Earth. Other factors, such as the energy lost while driving a shock, and/or the tension in magnetic field lines that might connect the CME to the Sun, could manifest themselves as an effective aerodynamic drag.

Spring 2011

Meets from 1:00-2:30 in Research I room 301.

May 3, 2011

Title: Photochemistry and Energetics of the ionosphere and thermosphere

Phil Richards, GMU

The energy that is deposited in the thermosphere and ionosphere by solar EUV photons ultimately ends up heating the ambient neutral gases through the complex set of ion and minor neutral chemical reactions. We summarize the current state of knowledge of the ionospheric and thermospheric chemistry. With the aid of the Field Line Interhemispheric Plasma (FLIP) model, we show that the latest chemical scheme, solar EUV irradiances, and MSIS thermosphere model can satisfactorily account for most solar cycle and seasonal variations in the daytime peak density of the midlatitude ionosphere during magnetically quiet periods. The model calculations also demonstrate the importance of vibrationally excited N2 in the ionosphere. It is particularly important in producing negative ionosphere storms and also helps explain the rapid recovery after storms.

April 19, 2011

The evolution of fast and slow CMEs in interplanetary space observed by STEREO, SOHO and SDO.

Alexis Rouillard, GMU / NRL

The STEREO mission allows detailed comparisons of white-light images of the solar wind (SECCHI experiment) with in-situ measurements (ACE, WIND or STEREO) to be performed. We will review the recent results of such comparisons. They confirm that the location, orientation and topology of the magnetic field inside Coronal Mass Ejections (CMEs) largely dictate the aspect of CMEs in white light images. SECCHI can be used to investigate the interaction between CMEs and the background solar wind during their propagation to 1AU. Combined images of the solar corona obtained by STEREO, SOHO and SDO also provide high-cadence, high-resolution observations of shock waves. We use the unprecedented and complimentary observations of a shock-sheath region tracked continuously from the Sun to 1AU during the 2010 April 3-5 period to investigate the onset of a Solar Energetic Particle Event (SEP). The spatial extent, radial coordinates, and speed of the driver are measured from SECCHI observations and used as inputs to a numerical simulation of the CME propagation in the background solar wind. The simulated magnetic and plasma properties of the shock and the sheath region at 1AU agree very well with those measured in situ at L1. These simulation results reveal that during this event, Earth and STEREO-B are magnetically connected to the eastern and western edges of the CME bow shock. The simulation shows that the nine hour delay of the estimated SEP release time relative to the eruption time of the ejecta corresponds to the time required by the shock to reach the magnetic field line connected to L1. The shock compression ratio is found to grow along the magnetic field line until the maximum flux of high-energy particles is reached and then levels off.

April 12, 2011

How and Why Does the Ionospheric Total Electron Content Vary?

Robert R. Meier1, Judith Lean2, John Emmert2, Michael Picone1

April 12, 2011

A new general linear model of ionospheric climatology is described that accounts simultaneously for the influences of solar and geomagnetic activity, oscillations at four frequencies and a secular trend. The model captures more than 98% of the variance in the daily-averaged, global total electron content (TEC) of the ionosphere derived from GPS observations during the 16 years from 1995 to 2010, and enables the reconstruction of TEC variations since 1950. Solar EUV irradiance variations are the dominant ionospheric influence, directly increasing TEC by as much as 40 TECU from solar activity minimum to maximum and producing additional 27-day fluctuations of as much as 15 TECU (in October 2003). The semiannual and annual oscillations are comparable in magnitude to the 27-day fluctuations, with (peak to valley) amplitudes that increase from a few TECU at low solar activity to ~17 TECU during solar activity maximum. The phase and amplitude of the semiannual oscillation are identical in the northern and southern hemispheres (and hence globally). In contrast, the annual oscillation is twice as large in the southern hemisphere (where it peaks in December-January) than in the northern hemisphere (where it peaks in April-May). Seasonal, semiannual and annual anomalies in TEC are direct effects of semiannual and annual oscillations produced by orbitally driven photoionizaion and thermospheric composition changes, not of corresponding oscillations in solar or geomagnetic activity. Geomagnetic influences on daily-averaged global electron densities are relatively modest, with the maximum effect a reduction of 11 TECU (in October 2003) and only 11 episodes in excess of 5 TECU depletions during the past 16 years. A statistically significant positive trend of 0.6 0.3 TECU (1016 electrons m–2) per decade is detected in the 15-year record.

1 SPACS, GMU

2 Space Science Division, NRL

April 5, 2011

Lara Waldrop

Remote sensing of neutral species abundance in the Earth’s upper thermosphere from ground- and space-based platforms

The density and composition of the terrestrial upper atmosphere are key state parameters whose knowledge is essential for accurate photochemical modeling, understanding responses to space weather events, assessing secular atmospheric evolution, and supporting magnetospheric imaging capabilities. However, the empirical quantification of the few neutral species that comprise the upper thermosphere and exosphere is notoriously challenging. During the decades-long absence of direct, in-situ mass-spectrometer measurements, attempts to infer neutral density routinely and reliably from ground-based instrumentation have been limited by both observational constraints and theoretical ambiguities. Recent advances in numerical models and experimental techniques, including the availability of satellite-based remote sensing measurements, have motivated renewed efforts toward estimation of these key parameters. In this talk, I will summarize the long-standing challenges of ground-based upper thermosphere remote sensing and describe several promising new techniques, combining multi-platform observations with state-of-the-art photochemical and radiative transfer models, with the goal of achieving self-consistent upper thermospheric state estimation on a routine basis.

March 29, 2011

Phillip C. Chamberlin, NASA/GSFC

SDO/EVE observations of EUV irradiance changes during solar flares, and what impact these changes have on the Earth’s Ionosphere and Thermosphere.

The Solar Dynamics Observatory (SDO) began normal operations in May 2010. Since then, the Extreme ultraviolet Variability Experiment (EVE) has been returning the most accurate solar XUV and EUV irradiance measurements (6.5-105 nm) every 10 seconds at almost 100% duty cycle. Having these high temporal resolution observations at good spectral resolution (0.1 nm) allows EVE to quantify the changes in the radiative output during solar flares, leading to new insights into the solar plasma’s thermal evolution at all stages of the flare. These changes in the solar EUV output then drive similar changes in the Earth’s Ionosphere and Thermosphere due to higher ionization rates and heating in these upper atmospheric layers. The presentation will not only present and discuss the new results of solar flare plasma evolution, but also how these changes can influence the Earth’s I/T system.

March 8, 2011

Journal club discussion of Image:Angeo-26-2.pdf and Image:2010JA015.pdf

March 1, 2011

John V. Shebalin, NASA JSC

Coherent Eigenmodes in MHD Turbulence

The statistical mechanics of Fourier models of ideal, homogeneous, incompressible magnetohydrodynamic (MHD) turbulence will be presented. Although statistical theory predicts that Fourier coefficients of fluid velocity and magnetic field areb zero-mean random variables, numerical simulations clearly show that certain coefficients have a non-zero mean value that can be very large compared to standard deviation, i.e., a coherent structure generally exists in MHD turbulence. An eigenanalysis of the system reveals eigenvariables that are generalizations of the Elsässer variables. When certain eigenvariables are large compared to others, coherent structure and broken ergodicity result. Relevance for dissipative magnetofluids will be discussed.

February 22, 2011

Dusan Odstrcil

Geore Mason University

Title: The first STEREO multi-event: Numerical simulation of coronal mass ejections (CMEs) launched on August 1, 2010

On 2010-08-01 at least four coronal mass ejections (CMEs) were observed by the Heliospheric Imagers (HIs) onboard STEREO spacecraft. These events originated at diff erent parts of the solar corona and generated complex scenario of four mutually interacting CMEs. Real-time prediction of the arrival times to Earth failed and it is difficult to associate feautures observed by HIs with their solar sources and impacts at apacecraft. We use the heliospheric code ENLIL to show the global solution for two di fferent scenarios using fitted CME parameters from coronagraph observations. We present the temporal pro files and synthetic white-light images that enables direct comparison with in-situ and remote observations.

February 8th, 2011

Steven Meier [8] Director, Division for Crosscutting Capability Demonstrations [9].

Suborbital Opportunities at NASA: Facilitated Access to the Space environment for Technology (FAST) and Commercial Reusable Suborbital Research (CRuSR)

Fall 2010

Meets from 12:00-1:00 in Research I room 302 (Except on Sept 14th, Oct 12th, Nov 9th we are in room 306 of Science and Tech I)

December 7, 2010

Rebekah Evans

George Mason University

Title: Coronal Heating by Surface Alfven Wave Damping: Implementation in MHD Modeling and Connection to Observations

We present results from the development of a solar wind model driven by Alfven waves with realistic damping mechanisms. We self-consistently introduce surface Alfven wave damping, which is characterized by transverse gradients in density. The plasma gradients set up a resonant layer, in which the waves dissipate energy to the wind. First, we applied surface Alfven wave damping in a solar wind model driven by a flat wave spectrum (van der Holst et al. 2010), and demonstrated its effect at the boundary of open and closed magnetic fields (Evans et al. 2010). Here we apply surface wave damping to a model which allows a Kolmogorov-type spectrum of Alfven waves to evolve in frequency space (Oran et al. 2010). We consider waves with frequencies lower than those damped in the chromosphere, and on the order of those dominating the heliosphere (0.0001 to 100 Hz). We provide wave dissipation as a function of frequency. We connect our modeling results to recent observations, including an estimation of resonant absorption damping by Verth, Terradas & Goossens (2010) and density and temperature distributions using differential emission measure tomography by Vasquez, Frazin & Manchester (2010), which we present as both direct and indirect evidence that this dissipation mechanism occurs and is important in the lower corona.

November 9, 2010

Vladimir Truhlik

Institute of Atmospheric Physics, Academy of Science Czech Republic

Title: Relating Solar-Wind and Plasmaspheric Parameters to Topside Ionospheric Parameters by Using a Multi-Satellite Comprehensive Database

The ionosphere and plasmasphere (inner magnetosphere) are very complicated coupled systems and their state highly depends on solar wind conditions. We employ a large database available from the Space Physics Data Facility (SPDF) at the Goddard Space Flight Center to study parameters in the upper F region and the topside ionosphere in relation to the Earth’s plasmasphere and the solar wind. The database comprises all available topside sounder data from the four Allouette/ISIS satellites, in-situ measurements made by Langmuir probes and ion mass spectrometers on the ISIS-1 and ISIS-2 satellites, plasmaspheric measurements made from the OGO-5, and Explorer 45 satellites as well as solar wind data primarily from the Wind satellite. We mainly focus (1) on the relation of the main ionospheric trough to the position of the plasmapause and (2) on the response of high latitude ionosphere to magnetic clouds detected in the solar wind. The main goal of this research is to establish links between features observed in the plasmasphere and solar wind and features observed in the upper ionosphere using the capability of the Goddard SPDF database. We also discuss a possible contribution to the IRI model.

October 26

Peter Williams

NASA/GSFC

Title: Supergranule Convection at Solar Minimum

As well as the outward transport of energy, the solar convection zone is responsible for generating the Sun’s magnetic field. Improving our understanding of solar convection may lead to improved solar dynamo models and better predictability of the solar cycle.

Supergranulation is a component of solar convection with cells approximately 35 Mm across that last for 1-2 days. They are well observed in Doppler data as features with a strong divergent flow (~300 m/s) and are the dominant characteristic of the chromospheric network seen in Ca II K images, where they play an important role in structuring the local magnetic field.

Our recent study of supergranulation uses Doppler images obtained from the Michelson Doppler Imager (MDI). Characteristics of supergranulation such as sizes, lifetimes and velocities have been studied for two years relating to two solar minima, times during which very few sunspots were present. Manifestations of supergranulation from data simulations as well as within other data sources are also described. Ongoing studies using Doppler data from the Helioseismic Magnetic Imager (HMI) aboard the Solar Dynamics Observatory (SDO) are presented, offering new insight into surface convection features at unprecedented clarity and resolution.

September 21

On the consistency of satellite measurements of thermospheric composition and solar EUV irradiance with Australian ionosonde electron density data

Phil Richards and Bob Meier

George Mason University

We use a comprehensive ionosphere model to demonstrate that the TIMED satellite measurements of solar EUV irradiances, neutral densities, and neutral temperatures are consistent with Australian ionosonde measurements of the electron density from 2002 to 2006. Our approach is to adjust the NRLMSISE-00 model neutral densities and temperature to determine the changes that are needed for the ionosphere model to reproduce the electron density. These model-derived neutral densities and temperatures are found to agree well with measurements of neutral densities and temperatures from the TIMED-GUVI instrument for both magnetically quiet and disturbed conditions. The model calculations also demonstrate the importance of vibrationally excited N2 in the ionosphere; particularly in producing negative ionosphere storms. This technique opens up the prospect of using the vast ionosonde database to improve temporal variations of empirical models of the thermosphere during magnetic storms.

September 14

Journal club discussion of “Spinning Motions in Coronal Cavities”, by Y.-M. Wang and G. Stenborg

Discussion led by Georgios Chintzoglou

Abstract: In movies made from Fe XII 19.5 nm images, coronal cavities that graze or are detached from the solar limb appear as continually spinning structures, with sky-plane projected flow speeds in the range 5-10 km s-1. These whirling motions often persist in the same sense for up to several days and provide strong evidence that the cavities and the immediatly surrounding streamer material have the form of helical flux ropes viewed along their axes. A pronounced bias toward spin in the equatorward direction is observed during 2008. We attribute this bias to the poleward concentration of the photospheric magnetic flux near sunspot minimum, which leads to asymmetric heating into an equatorward spinning motion when the loops pinch off to form a flux rope. As sunspot activity increases and the polar fields weaken, we expect the preferred direction of the spin to reverse.

September 7th

Journal club discussion of

Art mentioned this article [10]

Summer 2010

July 6th

Thanks to the development of space tourism, a new generation of unusually low cost, extremely high flight rate, suborbital vehicles is coming on line in 2011. All of these vehicles are capable of carrying experiments and experimenters into space at prices about 10x lower than conventional sounding rockets. To explore the specific applications of such vehicles for space physics purposes, and the kinds of vehicle attributes that best suit space physics applications, we will hold a small workshop at George Mason University in Fairfax on Friday, July 6th.

This workshop will begin at 9:30 a.m. and run until early afternoon. Briefings by Alan Stern will describe the capabilities of these vehicles. Following this, workshop participants will individually present and discuss concepts for space physics applications in auroral, ionospheric, magnetospheric, and heliospheric research.

The meeting organizers are Mike Summers (GMU) and Alan Stern. Lunch will be provided. Please indicate your interest my emailing us at either msummers@gmu.edu or astern2010@aol.com.

June 21st

Parallel, grid-adaptive simulations of astrophysical jet plasma

Dr. Zakaria Meliani

The computational effort involves the use of modern shock-capturing schemes exploited at very high effective resolutions. Our implementation in the AMRVAC code allows various schemes for hydro and magnetohydrodynamic applications. The governing equations of relativistic (magneto)hydrodynamics need accurate numerical treatment, fully obeying their conservation law nature in four-dimensional space-time. To make predictions for the long-term behavior of astrophysical jet flows, the use of parallelized, grid-adaptive software is a requirement, optimally exploiting modern high performance computing platforms. I will discuss the octree-based automated grid refinement (AMR) strategy, its parallel implementation, and provide quantitative information on its performance on some typical applications.

I will highlight recent results on the classification of the radio source galaxies according to the properties of the external medium and of the central engine. In fact, we elaborate a model of two-component jet induced by intrinsic features of the central engine (accretion disk + black hole). We demonstrate that two-component jets with high kinetic energy flux contribution from the inner jet are subject to the development of a relativistically enhanced, rotation-induced Rayleigh-Taylor type non-axisymmetric instability. This instability induces strong mixing between both components, decelerating the inner jet and leading to overall jet decollimation. This novel scenario of sudden jet deceleration and decollimation can explain the radio source Fanaroff-Riley dichotomy as a consequence of the efficiency of the central engine in launching the inner jet component vs. the outer jet component. We infer that the FRII/FRI transition, interpreted in our two-component jet scenario, occurs when the relative kinetic energy flux of the inner to the outer jet exceeds a critical ratio.

June 15th

Shin-Yi Su

Institute of Space Science, and Center for Space and Remote Sensing Research, National Central University, Chung-Li, Taiwan.

Equatorial-to-Middle Latitude Ionospheric Irregularities: Studies Using ROCSAT Data

Equatorial-to-middle latitude topside ionospheric ion density variations observed by ROCSAT-1 at the 600-km altitude have been studied to construct the global/seasonal/local-time distributions of the equatorial plasma depletion (plasma bubble) occurrence rates, and the low-to-middle latitude plasma enhancement (plasma blob) occurrence rates from 1999 to 2004 when the solar activities were moderate to high. The occurrence distributions of the two contrasting density irregularity structures indicate some complementary pattern in the latitudinal distribution. The seasonal/longitudinal (s/l) distributions of the equatorial density depletions have been studied extensively and the causes of such distributions have been proposed due to (1) the magnetic declination angle to affect the longitudinal gradient of the ionospheric conductivity across the sunset terminator, (2) the geographic location of the dip equator to affect the ionospheric seasonal density variation, and (3) the strength of the geomagnetic field at the dip equator to drive the over-all electrodynamics. In contrast, the study of the low-to-middle latitude density enhancements has just been started and the occurrence distribution only indicates that the maximum occurrence rates appear during the June solstice in both northern and southern hemispheres. Some occurrence dependence is noticed at longitude of large magnetic declination region, but the causal relationship between the equatorial density depletion and the density enhancement irregularities needs further investigation. Details of the global/seasonal/local-time distributions between the two different density irregularities are compared and the causes of the plasma enhancement irregularity structures are discussed.

Spring 2010

The weekly SWL meeting will be on Tuesdays from 10:30-12:00 am in room 301. The meeting will either be a journal club discussion, a faculty meeting, or a seminar. On the weeks that there is a Space Physics-related seminar hosted on Friday by the Physics department, we may cancel the SWL meeting.

May 18th

Prasad Subramanian

Driving Currents enclosed by Coronal Mass Ejections from the Sun

Indian Institute of Science Education and Research, Pune, India

It is well known that magnetic fields play a very important role in the solar corona. Appropriately enough, coronal magnetic field measurements are an area of intense research. However, somewhat strangely, there are not many measurements or realistic estimates of coronal currents. We present estimates of currents enclosed by coronal mass ejections. We envisage a scenario where the JXB forces associated with these currents are primarily responsible for driving them. We compare these current estimates with those at other levels in the solar atmosphere (i.e., at the photosophere and chromosphere).

May 7th

Holly R Gilbert

NASA/GSFC-6700

Solar Surface Phenomena Associated with Coronal Mass Ejections

Solar coronal mass ejections (CMEs) drive some of the most dramatic space weather events that impact the terrestrial environment. These explosive, energetic events are often associated with phenomena on the solar surface, such as flares, prominence eruptions, and large global waves traveling across the low corona and chromosphere. I will discuss the interesting relationship between prominences, which are relative cool, dense material suspended in the hot corona, and CMEs, which are manifestations of the destabilization of the corona. Additionally, I will discuss the nature of globally propagating chromospheric “waves”, which are chromospheric imprints of fast, CME-generated hydromagnetic waves propagating in the solar corona. Understanding the underlying physics involved with surface phenomena associated with CMEs leads to a more complete picture of how these eruptions are initiated and subsequently evolve.

April 27

Satellite Observations of Shuttle Plumes: Implications for Diffusion, Transport, and Polar Mesospheric Clouds

Robert R. Meier

George Mason University

The satellite-borne Global Ultraviolet Imager (GUVI) on the TIMED satellite has produced more than 20 images of NASA Space Shuttle main engine plumes in the lower thermosphere. These reveal atomic hydrogen and, by inference, water vapor transport over hemispherical-scale distances with speeds much faster than expected from models of thermospheric wind motions. Furthermore, the hydrogen expands at rates that exceed the horizontal diffusion speed at nominal plume altitudes of 104-112 km. Some of the plumes are transported to Polar Regions where they form Polar Mesospheric Clouds—thought by some to be a harbinger of global change in the upper atmosphere. I will present a number of GUVI images and discuss the problems they present to our understanding of the dynamics in the lower thermosphere.

April 20

Eileen Chollet

A Multi-Point Perspective on the Solar Wind at a Small Scale

While a broad-brush picture of the heliosphere is typically available for space weather prediction, key parameters can change significantly over a million-kilometer scale. In this presentation, I will discuss the importance of energetic particle predictions for space weather and delve into recent energetic particle transport modeling work which may substantially improve available predictions. Using joint data from the ACE, Wind and STEREO spacecraft, I will explore the limitations on these predictions created by sharp gradients in the energetic particle intensity. I will present the physical properties of these gradients and their relationship to both large-scale solar wind structures and turbulence.

April 13

Observation and modeling of the Earth-ionosphere cavity electromagnetic transverse resonance and variation of the D-region electron density near sunset – how lightning measurements contribute to improving the International Reference Ionosphere model –

Fernando Simões

NASA/GSFC, Heliophysics Science Division, Space Weather Laboratory

In the frame of the African Monsoon Multidisciplinary Analyses campaign, measurements of very low frequency electric fields were performed onboard a stratospheric balloon launched on 7 August 2006 from Niamey, Niger. During flight, numerous sferics were observed associated to lightning from active convective cells a few hundred kilometers from the balloon. Lightning data analysis shows the transverse mode mean frequency of the Earth-ionosphere cavity decreasing from ~2.4 to 2 kHz over a period of 1 h about sunset. The observed change of the transverse resonance near dusk can be fairly reproduced by an electromagnetic wave propagation model, which takes into account the D-region electron density variation predicted by the International Reference Ionosphere model. In this seminar we discuss the significance of lightning data analysis for the investigation of ionospheric processes, namely the dynamics of the D-region, and how ground and balloon lightning measurements can be combined with incoherent scatter radar, radar networks, and rockets for investigating electron density variability in the low ionosphere.

April 6

Rebekah M Evans

March 26

Note special date, time, and location: Room 134, Innovation Hall Friday, 11:30am-12:30pm

IBEX and tails

Edward Roelof

APL

Abstract will be posted at http://www.physics.gmu.edu/wiki/Seminars:Spring_2010

March 23rd

10am-11am b/c of CDS meeting. 5-minute presentations of what we are all working on.

March 9

5-minute presentations of what we are all working on.

Ken Dere

Brian Curtis

March 5

Note special date, time, and location: Room 134, Innovation Hall Friday, 11:30am-12:30pm

Mercury’s Magnetosphere after MESSENGER’s Three Flybys

James Slavin

NASA Goddard Space Flight

Abstract will be posted at http://www.physics.gmu.edu/wiki/Seminars:Spring_2010

January 26th

Lower Atmosphere Sources of Thermosphere Ionosphere Structure and Variability

Tim Fuller-Rowell

CIRES University of Colorado and NOAA Space Weather Prediction Center

The conventional sources of ionospheric structure and variability are changes in solar radiative output and geomagnetic activity, together with the subsequent response of the thermosphere and ionosphere system and interaction between the components. In the past, the extreme events of storms and flares have captured much of the interest, but most of the time there is not a flare or geomagnetic storm in progress, so it is predicting the day-to-day changes that are required, e.g. is the ionospheric total electron content going to be higher or lower tomorrow? With the recent development of whole atmosphere models (WAM), some attention is now being directed towards quantifying the impact of wave forcing from the lower atmosphere. Features such as the midnight temperature maximum can now be simulated realistically in WAM, and the physics behind the four-cell ionospheric and electrodynamic longitude structure is attracting significant interest. It has also been suggested that episodic lower atmosphere events, such as stratospheric sudden warmings (SSW), impose a strong signature on the ionosphere. A SSW can be simulated in WAM but following a real event will require data assimilation, in order to confirm a real physical connection between changes in the dynamics in the lower atmosphere and the thermosphere ionosphere response.

February 12

Note special date, time, and location: Room 134, Innovation Hall Friday, 11:30am-12:30pm

Dana Langope

Physics Department

Montana State University

Abstract will be posted at http://www.physics.gmu.edu/wiki/Seminars:Spring_2010

Fall, 2009

November 18th

Satellite based FUV observations and their applications

Yongliang Zhang

The Johns Hopkins University Applied Physics Laboratory

Satellite based far ultraviolet (FUV) observations provide a unique way to monitor conditions in the thermosphere, ionosphere and auroral particle precipitations. The major FUV emissions include Lyman alpha (121.6 nm), OI 130.4 nm, OI 135.6 nm, N2 LBHS (140.0-150. nm) and LBHL (165.0 nm-180 nm). We will discuss how the FUV data from TIMED/GUVI can be used to retrieve products for space weather studies, such as energy flux and mean energy of precipitating electrons, thermospheric neutral composition (O/N2 ratio), neutral density profiles, ionospheric density profiles, equatorial plasma bubbles, and solar EUV flux. The FUV measurements greatly benefit the near-real time space weather monitoring over a global scale and provide inputs for models such as IRI, TIMEGCM, etc.

November 17th

(Tuesday) 11 AM – 12 PM. Research 1 room 301

Mikhail Sitnov

APL

Empirical reconstruction of CME- and CIR-driven magnetic storms

A significant advance in the modeling of magnetic storms has become possible due to a dramatic increase of the number of in-situ measurements and a new generation of empirical geomagnetic field models that abandon the main limitation of the past models, their pre-defined modular structure. A new-generation model TS07D (http://geomag_field.jhuapl.edu/model/) employs the expansion of the magnetic field of equatorial currents into a series of basis functions, making the current distribution entirely determined by data. The evolution in time is reconstructed by fitting the model field with a subset of the 1995-2005 database sampled when the average solar wind electric field vBz, Sym-H index, and its time derivative were close to their values at the considered moment. To demonstrate the model performance we consider two events, the April 21-23, 2001 storm, caused by a coronal mass ejection and the March 8-11, 2008 storm, driven by a corotating interaction region. In the latter case the results of the out-of-sample validation using five THEMIS probes are shown. The results are also compared with geosynchronous, Image, and Iridium data.

November 11th

Larry Kepko

NASA/GSFC

Flow, aurora and Pi2 associations observed by THEMIS

It has been known for decades that auroral substorm onset occurs on (or at least near) the most equatorward auroral arc, which is thought to map to the near geosynchronous region. The lack of auroral signatures poleward of this arc prior to onset has been a major criticism of flow-burst driven models of substorm onset. The combined THEMIS 5 spacecraft in-situ and ground array measurements provide an unprecedented opportunity to examine the causal relationship between midtail plasma flows, aurora, and ground magnetic signatures. I first present an event from 2008 using multi-spectral all sky imager data from Gillam and in-situ data from THEMIS. The multispectral data indicate an equatorward moving auroral form prior to substorm onset. When this forms reaches the most equatorward arc, the arc brightens and an auroral substorm begins. The THEMIS data show fast Earthward flows prior to onset as well. I suggest that the results strongly support flow-burst driven models of magnetospheric activity. I discuss further the association of flow bursts and Pi2 pulsations, and discuss the possibility of using Pi2 waveforms to infer midtail reconnection dynamics.

November 2nd

Note special day, time, and location: Monday in room 306 of Science and Tech I at 1pm.

Combining Observations and Simulations to Advance our Understanding of Solar Eruptions

Noé Lugaz (Institute for Astronomy – University of Hawaii)

As solar cycle 24 slowly begins, thanks to the always-expanding float of satellites observing the Sun and the heliosphere, immense progresses can be expected in the forecasting and understanding of space weather, in particular regarding the initiation and propagation of coronal mass ejections (CMEs). To make a full use of the new observation capabilities, numerical simulations are often required, in particular to separate instrumental effects from the observed physical phenomena. This is particularly true for line-of-sight observations, such as coronagraphic and heliospheric images, as well as for in-situ measurements for complex series of CMEs. In this talk, I will discuss recent progresses in determining CME physical properties from white-light images, both in the corona (LASCO) and in the heliosphere (SECCHI) with the help of numerical magneto-hydrodynamics models. I will also discuss new geometrical models, which can give information about the azimuthal properties of CMEs from stereoscopic heliospheric observations, and, which could greatly improve the forecasting of CME hit/miss at Earth. Finally, I will also explore how MHD models can help explaining in situ measurements at 1 AU, from isolated and multiple CMEs.

October 28th

Christopher J. Mertens

NASA Langley Research Center, Hampton, Virginia, USA

Models of Atmospheric Response to Low- and High-Energy Particle Precipitation

Enhanced low-energy particle precipitation during solar-geomagnetic storms increases the ion concentrations in the ionosphere. The state of the ionospheric E-region, in particular, is governed by ion-neutral chemistry. During geomagnetic storms, auroral particle precipitation increases the ionization of the neutral atmosphere, producing vibrationally excited NO+ (i.e., NO+(v)) through fast exothermic ion-neutral chemical reactions, which emits in the 4.3 um spectral region. Since NO+ is the terminal E-region ion, by charge neutrality, NO+(v) 4.3 um emission is an excellent proxy suitable for characterizing storm-time enhancements to the E-region electron densities. Auroral nighttime infrared emission observed by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument onboard the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics (TIMED) satellite is used to develop an empirical model of geomagnetic storm enhancements to E-region electron densities. The empirical model is called STORM-E and will be incorporated into the International Reference Ionosphere (IRI). In the first half of the talk, STORM-E development is discussed and results during the Halloween 2003 storm period are presented.

The second half of the talk is focused on radiation exposure from high-energy particle precipitation on the atmosphere. Galactic cosmic rays (GCR) and solar energetic particles (SEP) are the primary sources of human exposure to high linear energy transfer (LET) radiation in the atmosphere. A prototype operational nowcast model of air-crew radiation exposure is currently under development. The model predicts air-crew radiation exposure levels from both GCR and SEP that may accompany solar storms. The new air-crew radiation exposure model is called the Nowcast of Atmospheric Ionizing Radiation for Aviation Safety (NAIRAS) model. NAIRAS will provide global, data-driven, real-time exposure predictions of biologically harmful radiation at aviation altitudes. Observations are utilized from the ground (neutron monitors), from the atmosphere (the NCEP Global Forecast System), and from space (NASA/ACE and NOAA/GOES). Radiation exposure rates are calculated using the NASA physics-based HZETRN (High Charge (Z) and Energy TRaNsport) code. An overview of the NAIRAS model is given and results during the Halloween 2003 storms are presented.

October 6th

(Note that this is a Tuesday)

Philip Judge

HAO/NCAR

Look what’s under the magnetic carpet! Solar physics’ key to open the corona: the chromosphere.

I will attempt to show why we can no longer just “brush the chromosphere under the carpet”, magnetic or otherwise, and ignore its importance either in a solar or plasma pnysics context. I hope to convince you that the chromosphere deserves to be studied by more than an interesting group of souls who have, like myself, long since lost their way, and become hopelessly entangled in one of the most awkward parts of the Sun.

September 30th

Antti Pulkkinen

Automatic determination of the conic coronal mass ejection model parameters

NASA/GSFC

Characterization of the three-dimensional structure of solar transients using incomplete plane of sky data is a difficult problem whose solutions have potential for societal benefit in terms of space weather applications. In this paper transients are characterized in three dimensions by means of conic coronal mass ejection (CME) approximation. A novel method for the automatic determination of cone model parameters from observed halo CMEs is introduced. The method uses both standard image processing techniques to extract the CME mass from white-light coronagraph images and a novel inversion routine providing the final cone parameters. A Bootstrap technique is used to provide model parameter distributions. When combined with heliospheric modeling, the cone model parameter distributions will provide direct means for ensemble predictions of transient propagation in the heliosphere.

An initial validation of the automatic method is carried by comparison to manually determined cone model parameters. It is shown using 14 halo CME events that there is reasonable agreement, especially between the heliocentric locations of the cones derived with the two methods. It is argued that both the heliocentric locations and the opening half-angles of the automatically determined cones may be more realistic than those obtained from the manual analysis.

September 9th

Modeling Solar Coronal Flux Tubes in 2-D with Non-Isotropic Conduction

Art Poland

George Mason University

Spring, 2009

May 12

“Temporal and Spatial Distribution of Metal Species in the Upper Atmosphere”

John Correira

Catholic University of America

ABSTRACT: Every day the Earth is bombarded by approximately 100 tons of meteoric material. Most of this material is completely ablated on atmospheric entry, resulting in a layer of atomic metals in the upper atmosphere between 70 km and 150 km. These neutral atoms are ionized by solar radiation and charge exchange with ambient ions. UV radiances from the Global Ozone Monitoring Experiment (GOME) spectrometer on the ERS-2 satellite are used to determine long-term dayside temporal and spatial variations of the total vertical column density below 795 km of the meteoric metal species Mg Iand Mg II in the upper atmosphere. A retrieval algorithm developed to determine magnesium column densities was applied to all available data from the years 1996-2001. Long term results show the middle latitude dayside Mg II peaks in total vertical content during the summer, while neutral Mg demonstrates a much more subtle maximum in summer. An analysis of spatial variations shows geospatial distributions are patchy, with local regions of increased column density. To study short term variations and the role of meteors showers a time dependent mass flux rate is calculated using published estimates of meteor stream mass densities and activity profiles. There appears to be little correlation between modeled meteor shower mass flux rates and changes in the observed Mg I and Mg II metal column densities.

 

May 5

“The Lunar Data Project – Resurrecting Data From the Apollo Program”

David Williams

NASA, Goddard Space Flight Center

ABSTRACT: Every NASA mission must have a detailed plan to archive the scientific data collected in a standard format before it ever leaves the launch pad, but this was not always the case. Back in the Apollo era, there was no systematic requirement to archive the data at all, and no guidelines as to what constituted a standard archive product or what formats were acceptable. As a result, the Apollo data received at the National Space Science Data Center, NASA’s archive located at Goddard Space Flight Center, were in many cases incomplete, not well documented, and on different media in various formats. The current collection of Apollo data at the NSSDC is housed on microfilm, microfiche, hard-copy documents and magnetic tape in UNIVAC, CDC 6600, EBSIDC and other obsolete formats. With the recent interest in returning ot the Moon we have undertaken the Lunar Data Project to restore these old Apollo data sets, some from instruments which operated on the Moon for 7 years, into standard digital formats for online distribution, as well as look for data that were never archived with NSSDC originally. We have had some success on both fronts, but as we get farther from the Apollo days, the data and the people with direct experience are becoming harder to find. We will discuss the history of the Apollo science program and our efforts to resurrect these old data for use in the current lunar exploration program.

April 28

“Probing Dark Matter Properties through Dynamics of the Galaxy and the Local Group”

Ed Shaya

University of Maryland

ABSTRACT: Some key parameters of Dark Matter (DM) can most accurately be measured in the very nearby universe because DM dominates the mass in the outer Milky Way (MW) and in the other galaxies of the Local Group. Soon, the distribution of DM will be quantified by study of dynamical processes observable in fine detail within these entities. Precise measurements of 3-D velocities for stars, coherent star streams, and stars in satellite stellar systems out to the edge of the Galaxy can reveal the detailed shape of the dark matter halo as well as the total mass of the Galaxy. Similarly, 3-D velocities of galaxies in the Local Group can reveal the masses of individual dominant galaxies, the mass of the Local Group in total, and the density of the more smoothly distributed warm and hot DM. NASA’s Space Interferometry Mission (SIM) will make measurements at the level of 2-3 microarcsec/yr per star and will provide us with the 2nd and 3rd dimensions of the velocity vectors of stars as faint as 20th mag. The specifics of these mass distributions, total mass-to-light ratios, clumpiness of the Galaxy potential, flatness of the halo, and cuspiness of galaxy cores provide the mass and nature of the dark matter particle(s), and test the standard model of cosmology on small scales.

April 21

“Whither the thermosphere? Climate change at the edge of space”

John T. Emmert

Naval Research Laboratory

ABSTRACT: The Earth’s thermosphere is the hot, thin, and partially ionized part of the atmosphere situated between altitudes of 90 and 800 km. Its high temperature is primarily due to absorption of solar extreme ultraviolet (EUV) radiation, which is balanced by radiative infrared cooling by carbon dioxide and other agents. The thermosphere exerts significant drag on orbiting spacecraft, which causes their orbits to decay at a rate proportional to the mass density of the ambient gas. Satellite tracking data thereby provide an extensive historical record of the thermosphere back to the dawn of the space age. Recent studies indicate that, after taking into account the strong influence of solar EUV variations, the thermosphere is slowly cooling and contracting, a trend that has important implications for orbit prediction and orbital debris management. In this presentation we review the structure and physics of the thermosphere and briefly describe how density is extracted from orbital tracking data. We then examine trends in thermospheric density, as well trends in other upper atmospheric properties, and discuss their interpretation.

 

April 14

“Connecting Stars (their planets), Galaxies, and the Universe in the Decade of Astrometry”

Rob Olling

University of Maryland

ABSTRACT: In the coming era of precision astrophysics, new telescopes on the ground and in space will provide many, many Terabytes of highly precise photometric and astrometric (positional) measurements. The job of astrophysicists is to turn those precise measurements into “highly accurate facts,” i.e. inferences with small systematic errors.

The accuracy of many astronomical inferences have been improving steadily over the last few decades: from factors of several to tens of percent. In the near-field, GAIA and SIM-Lite (hopefully) will push the accuracies to the sub-percent level, while the Planck mission will measure the Cosmic Microwave Background with similar accuracy. Many experiments aim to achieve similar accuracies in the intervening parts of the Universe.

I will briefly touch on several subjects:

– Briefly introduce the proposed SIM-Lite mission

– how to use millimag (0.1%) photometry to find transiting extra-solar planets with GAIA-like spacecraft and with my own LEAVITT design

– how to find solar-system analogs with astrometry

– how to perform cosmology in our own backyard with double stars

– how to obtain 1% geometric distances for galaxies in the Local Group (H_0)

April 7

“Numerical Simulation of Interplanetary Coronal Mass Ejections for Space Weather Prediction”

Dusan Odstrcil

University of Colorado, Boulder

ABSTRACT: Coronal mass ejections (CMEs) have been identified as a prime causal link between solar activity and large, non-recurrent, geomagnetic storms. Modeling of the origin of CMEs is still in the research phases and it is not expected that real events can be routinely simulated in near future. Therefore, we have developed an intermediate modeling system which uses fitted coronagraph observations, specifies 3D ejecta, and drives the 3D numerical magnetohydrodynamic code ENLIL which uses the WSA coronal maps for background solar wind. We simulated a number of heliospheric events selected by community campaigns which enabled us to analyze the match between different parameters predicted by the model and observed by spacecraft. Attention is given to development of tools facilitating prediction of solar wind parameters at planets and spacecraft.

 

March 24th

“The Solar Dynamics Observatory and the Wait for Solar Cycle 24”

W. Dean Pesnell

Goddard Space Flight Center

ABSTRACT: The Sun hiccups and satellites die. That is what NASA’s Living With a Star Program is all about. The Solar Dynamics Observatory (SDO) is the first Space Weather Mission in LWS. SDO’s main goal is to understand, driving towards a predictive capability, those solar variations that influence life on Earth and humanity’s technological systems. The SDO science investigations will determine how the Sun’s magnetic field is generated and structured, how this stored magnetic energy is released into the heliosphere and geospace as the solar wind, energetic particles, and variations in the solar irradiance. The SDO mission consists of three scientific investigations (AIA, EVE, and HMI), a spacecraft bus, and a dedicated Ka-band ground station to handle the 150 Mbps data flow. The science teams at LMSAL, LASP, and Stanford are responsible for processing, analyzing, distributing, and archiving the science data. We will talk about the building of SDO and the data and science it will provide to NASA. The late start of Solar Cycle 24 will allow SDO to measure a very interesting solar minimum period. In particular, helioseismic studies of the solar interior will benefit from the low activity that should still be present at the launch of SDO later this year.

March 17th

“Chasing Lightning: Sferics, Tweeks and Whistlers”

Phillip A. Webb (GSFC and UMBC/GEST)

Kathleen Franzen (INSPIRE)

Abstract: The visible flash that we see from lightning is only part of the story. Lightning generates electromagnetic emissions at other frequencies that can propagate hundreds or thousands of kilometers across the surface of the Earth in the form of special signals called “tweeks” and “sferics”. Some of these emissions can even travel tens of thousands of kilometers out into space before returning to the Earth as “whistlers”. The INSPIRE Project, Inc is a non-profit scientific and educational corporation whose original mission was to bring the excitement of observing these very low frequency (VLF) natural radio emissions to high school students and interested individuals. Since 1989, INSPIRE has provided specially designed VLF radio receiver kits to over 2,600 participants around the world. A number of these participants use the VLF data they collect in very creative projects that include fiction, music and art exhibitions. This presentation will provide an overview of lightning and the resulting VLF emissions, the INSPIRE program and the VLF receiver, and discuss experiences gained from using the INSPIRE VLF kits as the basis of an undergraduate course that was taught for the first time in the Fall 2008 semester at University of Maryland Baltimore County (UMBC).

February 24th

“A reinterpretation of the energy balance in EUV loops due to new results from Hinode-EIS”

Stephen Bradshaw (NASA/GSFC and GMU)

Abstract:

New observations made by the Hinode EUV Imaging Spectrometer have revealed persistent redshifts in solar active region loops in the temperature range $10^{5.6} \leq T \leq 10^{6.4}$~K. The presence of redshifts, interpreted as bulk downflows, indicates that the loops are undergoing radiative cooling rather than continuous heating. This has significant consequences for current ideas regarding the physics of the ubiquitous 1~MK loops observed by instruments such as TRACE and SoHO-EIT.

A new interpretation of the energy balance in such loops is presented with model results that are found to agree well with the observed redshifts.

February 10th

AGN jet interaction with ICM plasma: Kinetic effects and Thermal conduction

Fathalah Alouani Bibi (Physics and Astronomy Department, GMU)

Abstract: I will talk about some of my work prior to joining George Mason University. In particular, I will be talking about the importance of kinetic effects in electron transport and thermal conduction during the interaction of an AGN jet with inhomogeneous intra-cluster plasma. I will show some of the dynamics of cooling flow cluster and the role of AGN jets as a main heating source. I will also discuss the limitations of the classical Spitzer theory in cases of steep temperature gradients and in non-Maxwellian plasmas, and give some alternatives/corrections

 

February 3rd

Forward Modeling of Coronal Mass Ejections using STEREO-SECCHI Data

Abstract: I will present a forward modeling technique to reconstruct coronal mass ejections observed with the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) instruments package aboard the Solar Terrestrial Relations Observatory (STEREO). First, I will review the different techniques that can be used to reconstruct the 3D electron density of coronal structures such as CMEs. I will describe in more details the forward modeling method, which consists in fitting a geometric model of a flux rope to the observed images. Finally, I will present a survey of more than 30 CMEs studied with this technique.

Fall, 2008

November 18th

Flux Rope Instabilities at the Onset of CMEs

Bernhard Kliem

Mullard Space Science Lab, University College London, UK and Institute of Physics, University of Potsdam, Germany
Images of erupting prominences typically suggest the magnetic topology of a single line tied flux rope. Many prominence eruptions and CMEs begin with an approximately exponential rise, suggesting that an instability of a flux rope may occur at the onset of the eruptions. I will present numerical simulations of two relevant instabilities, the well-known helical kink instability and the torus instability, using the force-free line tied flux rope equilibrium by Titov and Demoulin as initial condition. The properties of these instabilities indicate which parameters of the initial configuration control whether the eruption stays confined or becomes ejective, evolves into a fast or a slow CME, shows strong or weak writhing. Exponential as well as power-law rise profiles can be modeled. Supporting quantitative comparison of the simulations with several well observed eruptions will be included.

October 21st

Interstellar neutrals in the heliospheric interface

Vladsilav Izmodenov

Univ of Moscow

Abstract

The heliospheric interface is the region where the solar wind meets the local interstellar cloud. The cloud is partly ionized and neutral component of the cloud penetrates into the heliosphere where it can be observed. New observational information as crossing of the heliospheric termination shock (TS) by both Voyagers, new SOHO/SWAN and Ulysses data as well as maps of the heliospheric ENA spectra that are expected from the Interstellar Boundary Explorer (IBEX) mission after its launch on October 19 2008 create new requirements and new challenges for modelling of the heliospheric interface. Modern kinetic-gasdynamic models of the SW/LIC interaction takes into account multi-component nature of both the solar wind and the interstellar medium. New results that include dynamic effects of the interstellar H atoms, the 11-year and latitudinal variations of the solar wind, interstellar and heliospheric magnetic fields will be discussed. Analysis of the constraints on the models, which follow from the TS crossing by Voyagers and other observational data, will be given in the paper. Theoretical predictions of the ENA fluxes that will be measured by IBEX will be provided.

September 30th

Physics of Solar and Stellar Coronal Heating

Vladimir Airapetian

GMU at NASA Goddard Space Flight Center

Since the discovery of the enigmatically hot layer in the Sun, the solar corona, the problem of its heating had remained elusive. Over the last 53 years we learned that the solar corona is not just hot “quiet” plasma, but a highly “emotional” place for the most violent eruptions in the solar system, occurring on scales from hundreds to hundreds of thousands of kilometers. The recent solar missions, SOHO, TRACE and Hinode provided crucial clues for resolving the long-standing problem of the solar coronal heating. Meanwhile the space missions, HST, Chandra, FUSE, XMM-Newton, have confirmed that hot and X-ray bright coronae exist not only in the Sun, but in stars ranging from young pre-main sequence stars to evolved giants. These new data raise one fundamental question in astrophysics: can the solar analogy be directly applied to other stars, and how do the underlying physical processes differ? In this review I will discuss recent observations of the solar and stellar coronae and the physical mechanisms involved in their heating.

September 23rd

Ulysses Observations of Periodic Structures in the Solar Wind Velocity

Christina Henderson

Christina Henderson will present a surface-level talk about her research. The talk is aimed at an undergraduate level with no prior knowledge of the Sun/Earth system. The talk is open to discussion.

George Mason University

As we bask in the warm glow of a summer day, we become intimately familiar with the constant output of solar photons. Thanks to deflection by the Earth’s magnetic field (called the magnetosphere), we are less intimately familiar with the constant outflow of solar plasma known as the solar wind. Spacecraft sitting outside the magnetosphere, however, can constantly measure properties of the solar wind such as the bulk velocity, magnetic field, and density. Ulysses is one such spacecraft. In this research, we use data gathered by Ulysses in its polar solar orbit over a span of 18 years from 1990 to 2008. We compute the power spectrum of the velocity, searching for periods in the range of 5- to 40-days, as these have the largest impact on predicting processes, like aurora, that occur in the Earth’s magnetosphere. We develop methods to see the periods as they change in time by computing many power spectra while stepping through the data; we call this the spectrogram. We are able to compare the spectrogram with calculations of the fundamental period and harmonics of a idealized sawtooth type solar wind. We conclude that many periods in the spectrogram of the Ulysses data are due to real physical processes and not artifacts of the numerical calculations, such as harmonics. 3-D solar wind simulation results can be compared with Ulysses data; we hope to learn what physical processes could be missing in the simulations.

September 16th

SECCHI View of CME Dynamics: Observations and Theory

Valbona Kunkel

George Mason University and NRL

The propagation of CMEs through the field of view of LASCO (2–30 Rs) has been extensively studied in the past 10 years. Based on theory-data comparison, it has been established that most, if not all, CMEs can be understood as erupting magnetic flux ropes and that the observed dynamics in this regime can be correctly described by the erupting flux rope model (Chen 1996). Until STEREO became available, CME dynamics were not observed and the EFR model has not been directly compared with data beyond 30 Rs. In this talk, I will discuss new SECCHI observations of CMEs and their dynamaics and extend the modeling of CME propagation to Hi 1 field of view (out to about 100 Rs projected). Four CMEs are discussed. It is shown that the erupting flux rope model is able to fit the observed height-time and velocity-time data throughout the EUVI-COR1-COR2-HI1 field of view. This suggests that the model correctly captures the main acceleration phase and the residual acceleration phase of CME dynamics, i.e., the forces acting on CMEs. It is found that significantly larger values of the drag coefficient in the model than previously used are required to fit both the COR1-COR2 data and HI1 data. This means that the extended field of view imposes stronger constraints on model parameters than previously thought, such as the drag coefficient and therefore the magnetic energy required to power the eruption and subsequent propagation.

 

September 9th

An analytical model unscrambling the inner state of CMEs based on the scale measurements in coronagraphs

Yuming WANG

George Mason University

An analytical model is proposed to unscramble two physical parameters, polytropic index $\Gamma$ and the non-force-free index $I_{nff}$, defined by $|f_{em}/f_{th}|$ where $f_{em}$ and $f_{th}$ are the Lorentz force and thermal pressure force respectively, of flux-rope CMEs based only on the scale measurements in coronagraphs. By applying this model to the 2007 October 8 CME, we find that (1) $\Gamma$ of the CME plasma decreased quickly from 1.35 at the beginning to 1.05 before it went beyond 15 Rs and then continuously approached to 1.0, and (2) $I_{nff}$ kept decreasing from nearly 1.0 to below 0.1 when the CME leading edge arived at about 70 Rs. The first result implies taht the plasma in this CME was heated throughout the interplanetary space, and the CME underwent a nearly isothermal process. The second result suggests that the CME was not force-free at the early phase, but it tended to approach the force-free state when it ran away from the Sun. Besides, the model predicts that, for an initially non-force-free flux rope, $\Gamma$ will be less than 4/3 if it reaches force-free state at infinite distance, and particularly, $\Gamma=1$ and the density at the flux rope axis must be larger than that at the boundary if the flux rope finally goes to a steady propagating and expanding state. We expect that this model has potential application to other researches where a flux rope is employed.

August 28th

Multi-dimensional representation of the ionosphere from GNSS, altimetry and COSMIC

M. Schmidt (1), C. Zeilhofer (1), D. Bilitza (2), C.K. Shum (3), J. Zhang (1), L.-C. Tsai (4)

(1) Deutsches Geodaetisches Forschungsinstitut (DGFI), Alfons-Goppel-Strasse 11, 80539 Muenchen, Germany (2) Heliospheric Physics Laboratory/GMU, NASA Goddard Space Flight Center, Greenbelt, Maryland, USA (3) Geodetic Science, School of Earth Sciences, The Ohio State University, 275 Mendenhall, 125 S Oval Mall, Columbus OH 43210, USA (4) Center for Space and Remote Sensing Research, National Central University, Taiwan

(schmidt@dgfi.badw.de, zeilhofer@dgfi.badw.de)

During the last decade various satellite missions have turned out to be promising tools for monitoring ionospheric parameters. Dual-frequency GNSS observations, e.g., can be used to determine the slant total electron content (STEC), i.e. the integral of the electron density along the ray-path of the signal between the transmitting satellite and a receiver. Furthermore, dual-frequency altimetry satellites allow measuring the vertical total electron content (VTEC).

In this contribution we present a multi-dimensional ionospheric model calculated from GNSS, altimetry and COSMIC measurements. To be more specific our model consists of a given reference part, computed from the International Reference Ionosphere (IRI), and an unknown correction term. Since the latter is represented as a series expansion in terms of multi-dimensional base functions, e.g., constructed from polynomial B-splines, trigonometric B-splines or spherical harmonics, our approach can be applied to global, regional and local data sets. The unknown series coefficients are calculable by applying parameter estimation procedures. Since the input data are heterogeneously sampled in space and in time due to the specific orbit and instrumental characteristics, finer structures of the target function are modelable just in regions with a sufficient number of observation sites.

Summer, 2008

Tuesday August 5th at 11 am in room 301

Space Weather research in South Africa

Lee-Anne McKinnell

Spring, 2008

Friday May 23rd at 11 am in room 302

Note special day, time, and room

Theoretical and Observational Constraints on Accretion Flows on Black Hole: The Case of sub-Keplerian Motion

Sandip K. Chakrabarti (1)

Senior Professor, S.N. Bose National Centre for Basic Sciences

Theoretically, matter enters into a black hole with velocity of light and thus every flow, independent of its past history, must be supersonic on the horizon. Not surprisingly, the transonic flow solutions respect such a boundary condition, even when it allows very exciting possibility that flows should pass through shocks and slow the matter down at a few Schwarzschild radii before the horizon. It is thus no surprise that ALL the observations (ranging from spectral state transition, Quasi-periodic oscillations, jets and outflows and non-thermal spectra from black holes) agree to the fact that such a Centrifugal Pressure Dominated Boundary Layer (CENBOL) should exist. There are several post-facto cartoon models in the literature which apparently have no knowledge of such beautiful behaviour of the flow and surprisingly come up with cartoon diagrams having the same behaviour. In our advective disk paradigm, jets are produced when CENBOL is present. Thus it no surprise that some post-facto models include the base of the jet (which is nothing but CENBOL in our picture) in explaining outgoing spectrum from disk surface and thereby creating a confusion that X-rays from the jets are also serious contestants. We show that for every observation that has been a pre-facto prediction of our paradigm of two component advective flow (TCAF). These are re-discovered by many in the literature under new names, pictures and models. What is more important, however, is that the theoretical solutions and the cartoons from fitting observational data are finally converging. This paves the way of further progress in the subject.

(1) Also, In Charge, Academic Affairs, Indian Centre for Space Physics, Kolkata

May 7th

Robert Duffin

George Mason University

Type III-L Solar Radio Bursts and their Correlations with Solar Energetic Proton Events

Abstract

Type III-L bursts are a sub-class of type III solar radio bursts that tend to occur after the impulsive phase of flares; are longer in duration than individual type IIIs and tend to be low-frequency. There has been a proposal that type III-Ls are connected to solar energetic proton (SEP) events. Most work on this connection has started from samples of SEP events, but if type III-Ls are to be useful for prediction of SEP events, then we need to understand the properties of samples of type III-L bursts. This talk reports preliminary results from such a study. An operating definition based on previous work is used to identify type III-L events amongst M- and X-class flares from 2001; and then correlations with other properties of these events are investigated, including association with SEP events. If there is a correlation with SEP events, one important factor that these bursts allow us to address is the question of whether acceleration takes place at an associated CME, or closer to the flare site well below the CME.

April 30th

Joseph Lazio

Naval Research Laboratory

The Dark Ages Lunar Interferometer (DALI)

The Dark Ages represent the last frontier in cosmology, the era between the genesis of the cosmic microwave background (CMB) at recombination and the formation of the first stars. During the Dark Ages, when the Universe was unlit by any star, the only detectable signal is likely to be that from neutral hydrogen (HI), which will appear in absorption against the CMB. The HI absorption represents potentially the richest of all data sets in cosmology—not only is the underlying physics relatively simple so that the Hi absorption can be used to constrain fundamental cosmological parameters in a manner similar to that of CMB observations, but the spectral nature of the signal allows the evolution of the Universe as a function of redshift (z) to be followed. The Hi absorption occurs in dark matter-dominated overdensities, locations that will later become the birthplaces of the first stars, so tracing this evolution will provide crucial insights into the properties of dark matter and potentially reveal aspects of cosmic inflation. Moreover, given the relatively simple physics—the Universal expansion, Compton scattering between CMB photons and residual electrons, and gravity—any deviation from the expected evolution would be a “clean” signature of fundamentally new physics.

The Dark Ages Lunar Interferometer (DALI) is a mission proposed for study to NASA for a telescope located on the far side of the Moon, the only site in the solar system shielded from human-generated interference and, at night, from solar radio emissions. The DALI array will observe at 3–30 m wavelengths (10–100 MHz; redshifts 15 \le z \le 150), and the DALI baseline concept builds on ground-based telescopes operating at similar wavelengths, e.g., the Long Wavelength Array (LWA) and Murchison Widefield Array (MWA). Specifically, the fundamental collecting element will be dipoles. The dipoles will be grouped into “stations,” deployed via rovers over an area of approximately 50 km in diameter to obtain the requisite angular resolution. The desired three-dimensional imaging requires approximately 1000 stations, each containing 100 dipoles (i.e., ~ 10^5 dipoles); alternate processing approaches may produce useful results with significantly fewer dipoles (factor ~ 3–10). Each station would be deployed by one rover, which would also serve as a “transmission hub” for sending the signals for correlation to a central processing facility. After sending the correlator output to Earth, analysis would then proceed via standard methods being developed for ground-based arrays.

 

Friday May 23rd at 11 am

Note special day and time

Theoretical and Observational Constraints on Accretion Flows on Black Hole: The Case of sub-Keplerian Motion

Sandip K. Chakrabarti (1)

Senior Professor, S.N. Bose National Centre for Basic Sciences

Theoretically, matter enters into a black hole with velocity of light and thus every flow, independent of its past history, must be supersonic on the horizon. Not surprisingly, the transonic flow solutions respect such a boundary condition, even when it allows very exciting possibility that flows should pass through shocks and slow the matter down at a few Schwarzschild radii before the horizon. It is thus no surprise that ALL the observations (ranging from spectral state transition, Quasi-periodic oscillations, jets and outflows and non-thermal spectra from black holes) agree to the fact that such a Centrifugal Pressure Dominated Boundary Layer (CENBOL) should exist. There are several post-facto cartoon models in the literature which apparently have no knowledge of such beautiful behaviour of the flow and surprisingly come up with cartoon diagrams having the same behaviour. In our advective disk paradigm, jets are produced when CENBOL is present. Thus it no surprise that some post-facto models include the base of the jet (which is nothing but CENBOL in our picture) in explaining outgoing spectrum from disk surface and thereby creating a confusion that X-rays from the jets are also serious contestants. We show that for every observation that has been a pre-facto prediction of our paradigm of two component advective flow (TCAF). These are re-discovered by many in the literature under new names, pictures and models. What is more important, however, is that the theoretical solutions and the cartoons from fitting observational data are finally converging. This paves the way of further progress in the subject.

(1) Also, In Charge, Academic Affairs, Indian Centre for Space Physics, Kolkata

May 7th

Robert Duffin

George Mason University

Type III-L Solar Radio Bursts and their Correlations with Solar Energetic Proton Events

Abstract

Type III-L bursts are a sub-class of type III solar radio bursts that tend to occur after the impulsive phase of flares; are longer in duration than individual type IIIs and tend to be low-frequency. There has been a proposal that type III-Ls are connected to solar energetic proton (SEP) events. Most work on this connection has started from samples of SEP events, but if type III-Ls are to be useful for prediction of SEP events, then we need to understand the properties of samples of type III-L bursts. This talk reports preliminary results from such a study. An operating definition based on previous work is used to identify type III-L events amongst M- and X-class flares from 2001; and then correlations with other properties of these events are investigated, including association with SEP events. If there is a correlation with SEP events, one important factor that these bursts allow us to address is the question of whether acceleration takes place at an associated CME, or closer to the flare site well below the CME.

April 30th

Joseph Lazio

Naval Research Laboratory

The Dark Ages Lunar Interferometer (DALI)

The Dark Ages represent the last frontier in cosmology, the era between the genesis of the cosmic microwave background (CMB) at recombination and the formation of the first stars. During the Dark Ages, when the Universe was unlit by any star, the only detectable signal is likely to be that from neutral hydrogen (HI), which will appear in absorption against the CMB. The HI absorption represents potentially the richest of all data sets in cosmology—not only is the underlying physics relatively simple so that the Hi absorption can be used to constrain fundamental cosmological parameters in a manner similar to that of CMB observations, but the spectral nature of the signal allows the evolution of the Universe as a function of redshift (z) to be followed. The Hi absorption occurs in dark matter-dominated overdensities, locations that will later become the birthplaces of the first stars, so tracing this evolution will provide crucial insights into the properties of dark matter and potentially reveal aspects of cosmic inflation. Moreover, given the relatively simple physics—the Universal expansion, Compton scattering between CMB photons and residual electrons, and gravity—any deviation from the expected evolution would be a “clean” signature of fundamentally new physics.

The Dark Ages Lunar Interferometer (DALI) is a mission proposed for study to NASA for a telescope located on the far side of the Moon, the only site in the solar system shielded from human-generated interference and, at night, from solar radio emissions. The DALI array will observe at 3–30 m wavelengths (10–100 MHz; redshifts 15 \le z \le 150), and the DALI baseline concept builds on ground-based telescopes operating at similar wavelengths, e.g., the Long Wavelength Array (LWA) and Murchison Widefield Array (MWA). Specifically, the fundamental collecting element will be dipoles. The dipoles will be grouped into “stations,” deployed via rovers over an area of approximately 50 km in diameter to obtain the requisite angular resolution. The desired three-dimensional imaging requires approximately 1000 stations, each containing 100 dipoles (i.e., ~ 10^5 dipoles); alternate processing approaches may produce useful results with significantly fewer dipoles (factor ~ 3–10). Each station would be deployed by one rover, which would also serve as a “transmission hub” for sending the signals for correlation to a central processing facility. After sending the correlator output to Earth, analysis would then proceed via standard methods being developed for ground-based arrays.

March 26th

Juan C Luna

George Mason University

The role of bulk and thermal Comptonization in producing the time lags observed in X-ray pulsars

Fourier analysis of X-ray pulsar data reveals the presence of time lags between hard and soft channels in millisecond pulsars. There is currently no consistent theoretical explanation for this effect based on a fundamental physical model for pulsar sources. In the proposed research, a new theoretical model is developed from first principles based on the bulk and thermal Comptonization occurring in the gas inside the accretion column above one (or both) of the magnetic poles on a rotating neutron star. The model utilizes a combination of Fourier and Laplace transformation in order to obtain quantitative predictions for the time lags. This approach will be used to make predictions about the possible presence of time lags in the spectra of bright pulsars such as Her X-1. Theoretical interpretation of the time lags can provide detailed information about the size and properties of the scattering plasma and also the spatial density profile of the scattering electrons.

March 19th

V. Truhlik

Institute of Atmospheric Physics, Prague, Czech Republic

Studying of solar activity variation of the electron temperature in the topside ionosphere

Electron temperature (Te) in the topside ionosphere and plasmasphere is an important parameter because thermal electrons play a key role in the energy balance of these regions. The IRI (International Reference ionosphere) model includes an empirical representation of Te in the topside ionosphere depending on altitude, latitude, local time, and season. But due to a lack of data and sometimes conflicting measurements, the solar activity variation of Te has not been reliably modeled so far.

We have made good progress in modeling the Te behavior with the help of a large database of satellite electron temperature measurements, and of Incoherent Scatter Radars observations, and with the assistance of simulations with the theoretical FLIP model. The presentation will focus in particular on (1) comparison of calculation of the FLIP model with data (2) latitudinal and altitudinal variation of Te and the heat flux (3) discussion prevailing cooling and heating terms influencing Te balance and causing its changing with solar activity. We will also discuss development of a new global Te model with the Te solar activity variation as a correction term which can help to improve current Te model in IRI.

February 20th

Phil Richards

George Mason University

Controversies in Solar EUV Irradiance and Ionospheric Photoelectron fluxes

For many years, there has been controversy over the magnitude of both the solar EUV (0-100 nm) irradiance and 0-1 keV photoelectron flux. The solar EUV irradiance is the primary driver of the energetics and dynamics of the Earth’s upper atmosphere above 100 km. There are uncertainties in theoretical photoelectron fluxes because of uncertainties in cross sections and solar EUV irradiance. Accurate solar EUV irradiance measurements are difficult to make because they must be made at high altitudes and because the energetic photons degrade the instruments that measure them. The ionization of oxygen and nitrogen in the upper atmosphere produces energetic photoelectrons as well as ions. Photoelectrons take approximately half the incident photon energy in the creation of secondary ions and electrons and airglow emissions. In recent years, the photoelectron flux has become important because the airglow emissions are heavily used in diagnosing variations in the upper atmosphere. This paper reexamines the consistency of solar EUV irradiance and ionospheric photoelectron fluxes using recent measurements.

February 13th

Geospace Imaging: The Big Picture

Bob Meier

George Mason University

Various regions of the geospace environment have been named and are often studied as if they exist in isolation. Yet emerging high quality multidisciplinary global datasets clearly demonstrate the complex and highly variable synergy among traditional space physics regimes. As a result, interdisciplinary endeavors, such as for example, magnetospheric-ionospheric coupling studies, are growing rapidly but face difficult challenges in understanding just how the various geospace regions interact. The recent progression of global imaging missions and the encouraging efforts to interface models of the various geospace regions give hope that one day we may actually be able to literally see “the big picture” that is crucial for understanding the space environment as a whole system. Ultimately we may be able to trace the paths of radiation and plasma eruptions from their origins at the Sun through to the responsive interactions among the magnetosphere, plasmasphere, ionosphere, and thermosphere. This lecture will trace the evolution of global imaging, from the initial measurements, to what we are learning now, to innovative prospects for developing new understanding from big pictures of the neutral and ionized components of geospace.

Fall, 2007

November 14th, 2007

Merging Galaxies: A Nearby Laboratory for High-Redshift Star Formation and Supermassive Black Holes

David Rupke

University of Maryland

drupke@astro.umd.edu

The rates of star formation and black hole activity in the universe peaked 10 billion years ago. The majority of this star formation occurred in dusty, merging galaxies, which in turn evolved into galaxies containing luminous black holes. Many examples of these dusty mergers occur in the local universe. I will review some of the unique properties of these local mergers, including morphologies, masses, gas dynamics, and heavy element content. I will place them both in the context of other galaxies in the local universe and in the context of their high-redshift counterparts.

November 7, 2007

Stephen Rinehart

NASA — Goddard Space Flight Center

Stephen.A.Rinehart@nasa.gov

From Spitzer to SPECS: The Future of Far-Infrared Astronomy

The development of infrared astronomy in the 20th century led to the discovery that the universe appears fundamentally different at long wavelengths. Missions such as the Infrared Astronomical Satellite (IRAS), the Infrared Space Observatory (ISO), and the Kuiper Airborne Observatory (KAO) have led to new understanding of the origins of galaxies, stars, and planets. Spitzer, currently on-orbit, has continued breaking new ground, and upcoming facilities such as the Herschel Space Telescope and the Stratospheric Observatory for Infrared Astronomy (SOFIA) promise to continue the legacy of their predecessors. As these missions move forward, we will develop the next generation of far-infrared observatories, taking advantage of new technologies and new techniques to address some of the most compelling astrophysical questions of our time.

October 31, 2007

Manolis K. Georgoulis

Johns Hopkins University/APL

http://sd-www.jhuapl.edu/FlareGenesis/Team/Manolis/

Progress and Challenges in the Analysis of Solar Vector Magnetograms: Why do we need these measurements, anyway?

Despite decades of ground-breaking advances in solar vector magnetography, vector magnetograms with a potential for meaningful science are routinely produced only within the last fifteen years or so. However, serious limitations in the acquisition of such pristine data result in an inherently incomplete physical understanding of the solar magnetized atmosphere. We are in urgent need of even this partial information because nearly every aspect of the long- or short-term evolution in the Sun stems from the emergence and evolution of solar magnetic fields. I will briefly review the current status of the analysis and the challenges pertaining to solar vector magnetograms. My main focus, however, will be on the new insight of the magnetic Sun that these measurements can help us gain. I will try to show that fitting even some pieces of the inextricable puzzle of solar magnetism can lead to substantial developments in the physical understanding of our magnetic star.

October 17th, 2007

The Angry Sun: Explosions in the Corona

James Klimchuk

james.klimchuk@nrl.navy.mil

Space Science Division, Naval Research Lab

Although the Sun is a benevolent provider of warmth and comfort, it also has a very angry side. Solar outbursts cause inclement space weather that sometimes wrecks havoc on technological systems on which our society is progressively more dependent. These outbursts involve the sudden release of energy that is stored in stressed coronal magnetic fields. They occur on a wide variety of scales. In this talk, I will discuss the smallest and largest events: nanoflares, which collectively heat the corona to multi-million degree temperatures and are responsible for the variable X-ray and UV radiation that modifies the Earth’s upper atmosphere; and coronal mass ejections (CMEs), which are spectacular eruptions responsible for the largest geomagnetic storms. I will present new observations from the recently launched Hinode and STEREO missions, and I will review the current state of theoretical understanding.

October 10, 2007

Seeing the Heliosphere with New Eyes: First Results from the SECCHI Experiment on STEREO

Angelos Vourlidas

SECCHI Project Scientist, Naval Research Laboratory

The STEREO mission was launched on October, 2006 with the main objective to study Coronal Mass Ejections (CMEs) from their initiation in the solar corona to their arrival at Earth using a suite of remote sensing and in-situ instruments on two, almost identical, spacecraft. The mission objectives are mainly addressed by the imaging experiment, named Sun-Earth Connection Coronal & Heliospheric Investigation (SECCHI), which comprises a suite of five telescopes; an EUVI full disk imager, two coronagraphs covering the range from 1.5 to 15 solar radii, and two heliospheric imagers observing along the Sun-Earth LINE from 15 solar radii to the Earth’s orbit and beyond. It is the first time that such imaging capabilities are available and they will certainly lead to important advances in our understanding of the CME initiation, propagation, and its three-dimensional configuration. In this talk, we will showcase the observations and initial results from the first months of operations of the SECCHI telescopes. We will also discuss the instrument performance and synergies with existing observatories (e.g., SOHO). SECCHI was built by a consortium of US and European institutions under the direction of the Solar Physics Branch at the U.S. Naval Research Laboratory.

October 3, 2007

New perspective on CME rates and their distributions: Lessons from CACTus (Computer Aided CME Tracking)

Eva Robbrecht

Eva.Robbrecht@oma.be

SIDC/Royal Observatory of Belgium

We present the first ‘objective’ LASCO CME catalog, a result of the application of the CACTus software on the LASCO archive during the interval September 1997 – January 2007. We have studied the CME characteristics over solar cycle 23 and have compared them with similar results obtained by manual detection (CDAW catalog).

The main results that I will discuss during my talk are:

I. There is a great discrepancy between CACTus and CDAW CME rates, both in shape and in amplitude. The CACTus statistics are dominated by narrow events that are mostly not included in the CDAW catalog.

II. While the classical CME picture is a white light structure having a typical angular width of 45° in the coronagraphic field of view, our catalog suggests that the CME process is scale invariant, i.e. that no typical CME size exists.

III. Are narrow CMEs witnessing the continuous renewal of the magnetic field? Are all plasma outflows an indication of the same physical mechanism?

IV. Our different CME statistics shed new light on the composition of CME (and other) catalogs and highlights the need for caution in the usage of catalogs. Perhaps the most revealing conclusion of this paper is that at present, no ‘ground truth’ CME catalog exists, since no consensus exists about the nature and origin of marginal coronal eruptions.

September 26, 2007

Reducing Parameter Estimation Bias in Empirical Models:�A Case for Data Assimilation in Radiation Belt Science

Josh Rigler, NCAR/HAO

jrigler@hao.ncar.edu

Leaving relevant variables out of a model will almost invariably lead to biased estimates of any empirical parameters required by the model, assuming that these parameters are optimized to somehow minimize the�discrepancy between model output and real data. Since this is quite often the case, the previous statement acknowledges formally what many modelers already understand intuitively: parameterized models that�ignore relevant physics tend to compensate by over- or under-stating the influence of whatever physics were actually included in the model.��

This raises the question of how one mitigates bias error so that the physics being modeled are most accurately portrayed? I present results from an ongoing study using data-derived radiation belt electron flux models, combined with a relatively simple data assimilation�technique. By simultaneously estimating its parameters, and correcting the model to better match observations, much correlated structure in the model residuals that causes bias error is removed, thereby providing more realistic parameter estimates. This a very general result, so similar results should be possible using any formal data assimilation scheme and empirical or semi-empirical model.

September 19, 2007

Global Hybrid Modeling of Magnetic and Energetic Particle Storms on the Magnetosphere

Farzad Kazeminezhad

West Virginia High Tech Consortium Foundation

farzad@wvhtf.org

A 2.5 dimensional hybrid model of massless fluid electrons and kinetic ions which also includes a simple ionosphere-magnetosphere coupling is used to investigate the impacts of interplanetary shocks and high energy particles presumably resulting from magnetic storms on the magnetosphere. The code is structured to model the magnetosphere dynamics of the Earth-Solar wind system by utilizing a finite element mesh specifically tailored to magnetosphere’s regions. It spans many hundred Earth radii in each direction (upstream, downstream, dawn and dusk). Realistic parameters characteristic of solar wind, its IMF and geomagnetic field are used. The code has been tested by its ability to predicting a magnetosphere by initializing a dipole at equilibrium with a flow subjected to an incoming solar wind with an IMF. The tests revealed generation of a steady state bow shock, as well as dayside reconnection (for southward IMF) as well as a tail sheet formation.

The interplanetary shock is generated by a sudden enhancement of the incoming IMF by an order of magnitude. This act introduced a fast MHD shock which propagated downstream and collided with the bow shock. This collision resulted not only in a steep rise in density and temperature of the bow shock, but also in the tail sheet region as the shock propagated downstream. The densities and temperatures, though, eventually relaxed to what are normal bow shock and tail values as the fast shock left the simulation domain. The sharp rise in the tail density which is insulated by geomagnetic field lines, can only be a result of kinetic effects. The results are analyzed and the role of different kinetic effects along with diagnostics discussed.

The high energy flux of particles are simulated by injecting Kev to Mev range particles. These particles are traced as their trajectories are stored. The deflection angle of the incoming particles versus their incident energies and their incident latitudes are obtained for the cases in which the incident IMF points north versus southward. Both these investigations are aimed at better understanding of the transport of energy and momentum by geomagnetic storms through their resulting interplanetary shock waves and high energy particles into the inner magnetosphere. This work is supported by the NSF-ATM-0651690.

September 12, 2007

Observations of Interplanetary Coronal Mass Ejections in the Inner Heliosphere Using Multiple Spacecraft

Ian Richardson

Astroparticle Physics Laboratory, NASA Goddard Space Flight Center

ianr@milkyway.gsfc.nasa.gov

Observations of interplanetary coronal mass ejections (ICMEs), the interplanetary counterparts of coronal mass ejections at the Sun, in the inner heliosphere during cycle 23 have largely been confined to the vicinity of Earth. However, in the mid-1970s to early 1980s, observations made by the Helios 1 and 2 spacecraft, in heliocentric orbits at 0.3-1 AU, together with observations near the Earth, provided a unique opportunity to investigate ICMEs and their associated shocks and energetic particle events at widely separated locations. With the recent launch of the STEREO spacecraft, and the SENTENELS mission under development, multi-point observations of interplanetary structures at <~ 1 AU will again be possible. The in-situ signatures of ICMEs will be reviewed, and results from earlier multi-point studies discussed, including their implications for these newer missions and space weather forecasting.

September 5, 2007

Living in an Asymmetric Solar System: What are we learning from the solar system final frontier

Merav Opher

George Mason University, 4400 University Drive, Fairfax, VA 22030

mopher@physics.gmu.edu

In the last couple of years we are having a flurry of activity at the edge of the solar system. After more than 30 years the twin Voyager spacecrafts arrived at the edge of the solar system and are sending back new data that are putting in putting in check old paradigms and forcing us to reexamine old theories. The twin spacecraft are probing the northern and southern hemispheres of the heliosphere providing us a stereo view. We showed recently (Opher et al. Science 2007; Opher et al. ApJL 2006) that only an asymmetric Solar system can explain the current data (radio emissions and streaming of low energy particles). Furthermore we were able to constrain the direction of the local interstellar magnetic field as not being in the plane of the disk of the galaxy (as was thought previously). This could be the first constrain of turbulence in the local interstellar medium in small scales. In this presentation I will review this findings, our present knowledge of the solar system final frontier and the current puzzles and open questions.

Spring, 2007

February 21, 2007

The CFD center at GMU

Rainald Lohner

Head, CFD Center Dept. of Computational and Data Sciences College of Sciences M.S. 6A2, George Mason University, Fairfax, VA 22030-4444, USA

An overview of the activities of the CFD center at GMU will be presented. Both the strategic application areas covered by the Center, as well as the fundamental and technical questions associated with them will be discussed. Current open questions will be discussed, as well as possible ways of resolving them.

Febrary 28, 2007

A Review of Atmospheric Flow and Dispersion Patterns

Fernando E. Camelli

Center for Computational Fluid Dynamics

Department of Computational Data Sciences

College of Sciences, George Mason University

fcamelli@gmu.edu

The application of Computational Fluid Dynamics (CFD) for transport and dispersion of pollutants in the urban scales has increased in the last decade. Improvement in computer performance is one of the pivotal reasons for this growing interest in using CFD with this type of application. In addition, the threat of an intentional chemical/biological/nuclear (CBN) release in a densely populated urban area has sparked research on dispersion patterns in urban scales for the past decade. The research of gas dispersion for scales larger than a city has been the focus of study for decades now, and Gaussian models have been the most successfully applied to these large scales. Unfortunately, the simpler models have been unable to reproduce and capture all the complex processes at an urban level. The reason for this failure is primarily the inability to represent the mechanical forces (i.e. building geometry, trees, traffic) and the thermal forces (i.e. surface heating, HAVC systems) that control dispersion at this scale level. Dispersion models that use first principle physics are available today as a direct result of the sustained increase of computational ability, thus allowing the performance of more operations in less time. This talk will review a Computational Fluid Dynamics (CFD) model called FEFLO-URBAN used to accurately calculate in time the flow field inside an urban layout. The transport and dispersion of a passive release is incorporated using an Eulerian framework. Five different scenarios will be presented: first, a realistic urban setting in Northern Virginia where the building geometry was obtained through blueprints (commercial development at Tysons Corner); second, the MUST experiment conducted in the U.S. Army Dugway Proving Ground Horizontal Grid test site in Utah; third, a scenario in New York City using FEFLO-URBAN as part of a collaborative effort supporting the design of the upcoming experiment in the Madison Square Garden area; fourth, the study of assessing maximum possible damage for contaminant release events in a generic subway station; and finally, the transport and dispersion problem around ship vessels, studying the flow patterns for the LPD17 and the concentration levels for the T-AKE 1. Discussion of last two seminars and handout

March 21, 2007

Comparative studies of multi-scale convective transport through the Earth’s plasma sheet

Timothy B. Guild

The Aerospace Corporation

Space Sciences Department/Chantilly

In this talk we will explore multi-scale, convective transport through the Earth’s plasma sheet using in situ observations and global terrestrial magnetospheric simulations. We statistically test the Lyon-Fedder-Mobarry (LFM) global magnetohydrodynamic (MHD) model with observations from the Geotail spacecraft at a variety of spatial and temporal scales within the plasma sheet. These comparisons illuminate model shortcomings and highlight the additional physics necessary to resolve data/model discrepancies. Specifically, we will describe comparisons of global-scale plasma moments, magnetic fields, and bulk flows within the plasma sheet. By characterizing the LFM plasma sheet velocity distribution as a function of simulation resolution, we find that increased resolution inherently changes the nature of the dynamics and transport within the LFM plasma sheet, bringing it into closer agreement with magnetotail observations containing fast, localized bulk flows. Due to the importance of these fast flows to mass, momentum, and energy transport in both the observed and simulated plasma sheets, we use the LFM to establish that locally-reconnecting magnetic lobe field lines initiate these simulated “flow channels”, explore the physical processes governing their subsequent evolution, and examine their similarity to observations of bursty bulk flows.

March 28, 2007

Self-Organized Criticality in a Numerical MHD Current Sheet with Cross-Scale Coupling to a Current-Driven Kinetic Instability

Alex Klimas

NASA, Goddard Space Flight Center

alex.klimas@nasa.gov 301-286-3682

Through analyses due to Uritsky et al. [JGR, 2002; GRL, 2003, 2006] of Polar UVI auroral emissions data, it is now well established that regions of bright UV emissions in the night-side aurora exhibit the properties of avalanches in a system in SOC. Based on the observed relationship between localized reconnection in Earth’s magnetotail and consequent auroral UV emissions, on the large range of emissions scales plus the necessary excitation energy, neither of which can have their origins in the ionosphere, and on various analogies between the driving and dissipation of sandpile SOC models and the loading and unloading of magnetic flux/energy in the magnetotail, Uritsky et al. and Klimas et al. [JGR, 2004] have suggested that the auroral dynamics is a reflection of the reconnection dynamics of the magnetotail, which is in or near a self-organized critical state. A study of reconnection in a 2-D current-sheet model containing coupled resistive MHD and kinetic-micro turbulence components will be discussed. The current sheet supports a magnetic field reversal and is configured so that under steady loading at its boundaries an equilibrium state can be reached in which the rate at which magnetic flux is driven into the reversal is balanced by the rate at which it is dissipated through annihilation. The transport of electromagnetic (primarily magnetic) energy carried by the Poynting flux into the reconnection region of the model has been examined. It has been shown that the Poynting flux evolves through bursts of avalanching activity separated by quiet times during which the current sheet recovers. All of the analysis techniques (and more) that have been applied to the auroral image data have also been applied to this Poynting flux. New results will be presented showing that the Poynting flux exhibits so many of the key properties of systems in self-organized criticality that an alternate interpretation is implausible. A strong correlation between these key properties of the model and those of the auroral UV emissions will be demonstrated. We suggest that, in general, the driven reconnection model is an important step toward a realistic plasma physical model of self-organized criticality and we conclude, more specifically, that it is also a step in the right direction toward modeling the multiscale reconnection dynamics of the magnetotail.

May 2, 2007

The International Reference Ionosphere – Climatological standard for the ionosphere

Dieter Bilitza

Raytheon IIS, GSFC, Space Physics Data Facility, Code 672, Greenbelt, MD 20771

Dieter.Bilitza.1@gsfc.nasa.gov

The International Reference Ionosphere (IRI) a joint project of URSI and COSPAR is the defacto standard for a climatological specification of ionospheric parameters. IRI is based on a wide range of ground and space data and has been steadily improved since its inception in 1969 with the ever-increasing volume of ionospheric data and with better mathematical descriptions of the observed global and temporal variation patterns. The IRI model has been validated with a large amount of data including data from the most recent ionospheric satellites (KOMPSAT, ROCSAT and TIMED) and data from global network of ionosondes. This talk will give an overview over the IRI effort with special emphasis on the activities that are currently in progress. I will discuss the latest version of the IRI model, IRI-2007, highlighting the most recent changes and additions. Finally, the talk will review some of the applications of the IRI model.

Journal Club

Fall 2012

The SWL journal club will meet ad-hoc on Tuesdays 1:00 pm – 2:30 pm in a room that will change from week-to-week. To receive announcements, register for the SWL student email list given at http://aurora.gmu.edu/spaceweather/index.php/Main_Page

Astrophysics Journal Club: This fall, the journal club will meet on alternate Wednesdays (Sep 5, 19; Oct 3, 17, 31; Nov 14, 28) from 3:00pm to 4:00pm in Planetary Hall (S&T I) room 306.

Spring, 2012

The SWL journal club will meet ad-hoc on Tuesdays 1:00 pm – 2:30 pm in Research Hall 302. To receive announcements, register for the SWL student email list given at http://aurora.gmu.edu/spaceweather/index.php/Main_Page

Astrophysics Journal Club: Jan 25; Feb 8, 22; March 7, 21; April 4, 18; May 2 from 1:30pm to 2:30pm in S&T I, room 306. To receive announcements, contact Joseph Weingartner joe@physics.gmu.edu.

Fall, 2011

The SWL journal club will meet ad-hoc on Tuesdays from 12:00-1:00pm.

During the fall 2011 semester, the astrophysics journal club will meet on alternate Wednesdays (Sep 7, 21; Oct 5, 19; Nov 2, 16, 30) from 1:30pm to 2:30pm in S&T I, room 306.

Spring, 2011

The SWL journal club will meet ad-hoc on Tuesdays from 1:00-2:00. To receive announcements, register for the SWL student email list given at http://aurora.gmu.edu/spaceweather/index.php/Main_Page

The Astronomy journal club’s first meeting of the semester is Wednesday, Jan 26 at 3:30 in S&T I, room 306. Suggested papers can be found on the web site: http://physics.gmu.edu/~joe/jc.html

Fall, 2010

The SWL journal club will meet ad-hoc on Tuesdays from 12:00-1:00. To receive announcements, register for the SWL student email list given at http://aurora.gmu.edu/spaceweather/index.php/Main_Page

The Astronomy journal club web site is http://physics.gmu.edu/~joe/jc.html

Spring, 2010

The SWL journal club will meet ad-hoc on Tuesdays from 10:30-11:30. To receive announcements, register for the SWL student email list given at http://aurora.gmu.edu/spaceweather/index.php/Main_Page

The Astronomy journal club will meet on alternate Wednesdays at 12:30 in S&T I, room 306 starting next on Jan 20. Suggested papers can be found on the web site: http://physics.gmu.edu/~joe/jc.html

Fall, 2009

Sept. 29th

  • Roundtable discussions of Graduate Work.

Sept. 22nd

  • Yod Poomvises will discuss his research
  • Title: CME propagation and expansion in 3-D space in the heliosphere based on STEREO/SECCHI observations.
  • Abstract: We report a study of kinematics and morphological evolution of CMEs by using STEREO/SECCHI observation to track in 3-D space a set of well observed events from the sun to a large distance in the heliosphere. The CME tracking is based on the Raytrace model (Thernisien et al 2006), which is able to represent a CME as a 3-D flux rope in the upper portion and two straight legs in the lower portion. The true 3-D location can be obtained. We are able to further calculate 3D velocity and 3D acceleration of CMEs free of project effect. In particular, the true cross-section of CMEs, and thus the expansion speed can be found. For the 5 events studied, we find that their bulk velocities eventually converge into a narrow range of 190 km/s – 430 km/s, while their initial velocities range from about 150 km/s to 1500 km/s. Their expansion velocities also converge into a narrow range between 140 km/s and 300 km/s. We find that the deceleration for fast events and acceleration for slow events mainly occur within 40 solar radii.

Sept. 15th

Spring, 2009

  • Meeting Time: 10:30 – 11:30 AM Tuesdays
  • Room 302

Mar. 31, 2009

Mar. 3, 2009

  • On Formation of a Shock Wave in Front of a Coronal Mass Ejection With Velocity Exceeding the Critical One
  • Author: M.V. Eselevich and V.G. Eselevich, Geophysical Research Letter, Vol. 35, L22105, doi:10.1029/2008GRL035482, 2008
  • Host: Indrajit Das

Feb. 17, 2009

  • Processes and Mechanisms Governing the Initiation and Propagation of CMEs
  • B. Vrsnak. Annales Geophysicae,. 26, 3089-3101, 2008
  • Download: [11]
  • HOST: Oscar Olmedo

Fall, 2008

  • New Meeting Time 3:00-4:00PM Tuesdays
  • Room 301

Oct 14th

Particle Acceleration at Perpendicular Shocks

  • Zank et al., 2005 | DIRECT DOWNLOAD:PDF Document
  • HOST: Oscar Olmedo

Sep 2

Multiscale modeling of magnetospheric reconnection

  • Kuznetsova et. al., 2007 | DIRECT DOWNLOAD:PDF Document
  • HOST: Rebekah Evans

 Summer, 2008

Aug 12

Solar excursion phases during the last 14 solar cycles

  • Mursula and Zieger, 1998 | DIRECT DOWNLOAD: PDF Document
  • HOST: Christy Henderson

July 29

Characteristic magnetic field and speed properties of interplanetary coronal mass ejections and their sheath regions

  • Owens et al., 2005 | DIRECT DOWNLOAD:PDF Document
  • HOST: Yod Poomvises

July 15

NUMERICAL INVESTIGATION OF THE HOMOLOGOUS CORONAL MASS EJECTION EVENTS FROM ACTIVE REGION 9236

July 1

Spring, 2008

June 3rd

May 12th

April 28th

Fall, 2007

There are two Journal Clubs this semester: A Joint Space Weather Journal Club and the Astrophysics Journal Club and a stand-alone Space Weather Journal Club. The joint journal club meets every other week (generally in SUB II). Seehttp://physics.gmu.edu/~mjordan/AJC.html for links to papers. The stand-along club meets intermittenly in the off weeks (generally in Res. I, room 301).

  • September 12 (Room: SUB II room 5)
    • “Implications of Interstellar Dust and Interstellar Magnetic Field at the Heliosphere”, P.C.Frisch,July 23, 2007 astro-ph arXiv:0707.2970v2
    • “The radius and mass or the subgiant star beta Hyi from interferometry and asteroseismology”, J. R. North, et al, MNRAS 380, L80-L83 (2007)
    • “The Orientation of the Local Interstellar Magnetic Field”, M. Opher, et al, Science 11 May 2007 316:875-878
    • “NGC 4254: An act of harrassment uncovered by the Arecibo Legacy Fast ALFA survey”, M.P. Haynes, et al, ApJ 665: L19-L22, 2007 August 10
    • “Optically unseen H1 detections towards the Virgo Cluster detedted in the Arecibo Legacy Fast ALFA survey”, B.R. Kent, et al, ApJ 665: L15-L18, 2007 August 10
  • September 26 (Room: SUB II room 5)
    • TBD
  • October 10 (Room: SUB II room 4)
    • TBD
  • October 31 (Room: SUB II room 6)
    • TBD
  • November 14 (Room: SUB II room 4)
    • TBD
  • November 28 (Room: SUB II room 4)
    • TBD
  • December 5 (Room: SUB II room 4)
    • TBD

Spring, 2007

Space Weather Journal Club

  • January 23: Yuming Wang : “Geomagnetic storms caused by compressed structures”
  • January 30: Yong Liu: “Ion Thermalization and Wave Excitation Downstream of Earth’s Quasiperpendicular and Marginally Supercritical Bow Shock”
  • February 06: Yong Liu – second part
  • February 13: Bob Weigel “Ring Currents”
  • February 20: Ken Dere
  • Feburary 27: Art Poland
  • March 06: Merav Opher “Magnetic Effects in the Heliosphere”
  • March 13: NOTE: Spring Break
  • March 20: Bob Meier
  • March 27: Dimitris Vassilliadis
  • April 03: I will not be here – passover TBD
  • April 10: Christy
  • April 17: canceled
  • April 24: Yod: “The Association of CME with their effects near Earth” by R. Schwenn et al (2005)
  • May 01: Oscar Olmedo
  • May 08: Rebekah Evans
  • May 15: Jim Chen
  • May 22: AGU-joint assembly
  • May 29 – last seminar before the summer
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