Student poster at COS Undergraduate Research Colloquium

Student poster at COS Undergraduate Research Colloquium

The focus of our project was an investigation into fluctuations and oscillations in the brightness of images of the solar corona, the outermost layer of the Sun’s atmosphere. Previous research has shown that power spectra computed from time series of light intensity values from the solar corona can be modelled by a general background power law, representing a combination of stochastic processes, with an added ‘tail’ at high frequencies, which captures a transition to white noise. Recently, work by Ireland et al. (2015) has proposed a more comprehensive spectral model that includes an additional superimposed Gaussian component to capture periodic spectral features. We use this comprehensive spectral model to perform the first global survey of power spectra of the extreme ultraviolet (EUV) solar corona. The solar region used is a massive (1000×1000-arcsecond) region, corresponding to 35% of the visible solar disk, and data from five wavelengths are considered: 171Å, 193Å, 211Å, 304Å, and 1600Å. The different wavelengths correspond to observations at different heights from the solar surface. We find that for these wavelengths, the best-fit model parameters distinctly reflect the regions’ visually observed features and allow for insight into the dynamical processes thought to exist in the solar corona. We …

Student Paper: Nonparametric causal inference for bivariate time serie

James M. McCracken and Robert S. Weigel

Phys. Rev. E 93, 022207 – Published 8 February 2016

We introduce new quantities for exploratory causal inference between bivariate time series. The quantities, called penchants and leanings, are computationally straightforward to apply, follow directly from assumptions of probabilistic causality, do not depend on any assumed models for the time series generating process, and do not rely on any embedding procedures; these features may provide a clearer interpretation of the results than those from existing time series causality tools. The penchant and leaning are computed based on a structured method for computing probabilities.

Student Article: History’s Greatest Comet Finder

By Karl Battams (a scientist at NRL who is doing a PhD with a concentration in Space Weather at GMU)

I have a curious claim to fame. I have almost certainly seen more individual images of comets than any person in history. A good ballpark estimate would be around 50,000 unique images of comets, but that may be slightly on the low side. Either way, it’s a lot.

More …

Student Paper: Convergent cross-mapping and pairwise asymmetric inference

Student Paper: Convergent cross-mapping and pairwise asymmetric inference

http://journals.aps.org/pre/abstract/10.1103/PhysRevE.90.062903

James M. McCracken and Robert S. Weigel

Convergent cross-mapping (CCM) is a technique for computing specific kinds of correlations between sets of times series. It was introduced by Sugihara et al. [Science 338, 496 (2012).] and is reported to be “a necessary condition for causation” capable of distinguishing causality from standard correlation. We show that the relationships between CCM correlations proposed by Sugihara et al. do not, in general, agree with intuitive concepts of “driving” and as such should not be considered indicative of causality. It is shown that the fact that the CCM algorithm implies causality is a function of system parameters for simple linear and nonlinear systems. For example, in a RL circuit, both voltage and current can be identified as the driver depending on the frequency of the source voltage. It is shown that the CCM algorithm, however, can be modified to identify relationships between pairs of time series that are consistent with intuition for the considered example systems for which CCM causality analysis provided nonintuitive driver identifications. This modification of the CCM algorithm is introduced as “pairwise asymmetric inference” (PAI) and examples of its use are presented.

Student Paper: Removal of pseudo-convergence in coplanar and near-coplanar Riemann problems of ideal magnetohydrodynamics solved using finite volume schemes

A.D. Kercher and R.S. Weigel

http://www.sciencedirect.com/science/article/pii/S002199911400789X

Numerical schemes for ideal magnetohydrodynamics (MHD) that are based on the standard finite volume method (FVM) exhibit pseudo-convergence in which irregular structures no longer exist only after heavy grid refinement. We describe a method for obtaining solutions for coplanar and near-coplanar cases that consist of only regular structures, independent of grid refinement. The method, referred to as Compound Wave Modification (CWM), involves removing the flux associated with non-regular structures and can be used for simulations in two- and three-dimensions because it does not require explicitly tracking an Alfvén wave. For a near-coplanar case, and for grids with 213 points or less, we find root-square-mean-errors (RMSEs) that are as much as 6 times smaller. For the coplanar case, in which non-regular structures will exist at all levels of grid refinement for standard FVMs, the RMSE is as much as 25 times smaller.

Stream Processing for Solar Physics Paper

Stream Processing for Solar Physics Paper

Karl Battams: http://arxiv.org/abs/1409.8166

Modern advances in space technology have enabled the capture and recording of unprecedented volumes of data. In the field of solar physics this is most readily apparent with the advent of the Solar Dynamics Observatory (SDO), which returns in excess of 1 terabyte of data daily. While we now have sufficient capability to capture, transmit and store this information, the solar physics community now faces the new challenge of analysis and mining of high-volume and potentially boundless data sets such as this: a task known to the computer science community as stream mining. In this paper, we survey existing and established stream mining methods in the context of solar physics, with a goal of providing an introductory overview of stream mining algorithms employed by the computer science fields. We consider key concepts surrounding stream mining that are applicable to solar physics, outlining existing algorithms developed to address this problem in other fields of study, and discuss their applicability to massive solar data sets. We also discuss the considerations and trade-offs that may need to be made when applying stream mining methods to solar data. We find that while no one single solution is readily available, many of the …

Dissertation Completion Awards – Spring 2014

Dissertation Completion Awards – Spring 2014

To All,
If your PhD student are planning to finish this upcoming Spring 2014 semester and you might need the Completion Award.  Please let Bob  know and please send us a statement tell us something about the student’s research and a note stating that the student is on track to finish his/her degree in the Spring 2014 semester.

see email from Cody Edwards

Dear colleagues,

I am happy to be able to deliver some good news regarding funding and one of our popular graduate support programs.  After much work (thanks to Amy and Renate), we have funding available to offer dissertation completion grants for spring 2014.  To be eligible, a student must be graduating in spring 2014 or summer 2014.  Further, by accepting the grant, awardees are agreeing to discontinue any work assignment or position currently held and not to accept any work assignment during the spring 2014 semester (assistantships, teaching responsibilities, off-campus jobs, etc.).  Awards will be in the amount of $8,000.  If awardees are enrolled in the Subsidized Graduate Health Insurance plan, they will maintain their policies for the duration of the plan year.  If they were eligible for the In-State Tuition Eligibility Policy during the fall semester, their tuition will revert to Out-of-State rates for the spring semester.  However, awardees …

Research initiatives for physics grad students- August 5, 2013

Research initiatives for physics grad students- August 5, 2013

We are working with the Office of Equity and Diversity Services to develop a plan to increase the number of underrepresented minorities in physics at all levels. We are meeting with Corey Jackson on the 20th of August to discuss our plans.

Local High School Science Fair Winner on Space Weather Investigation!

A local high school student, Sahana Rao, from Centreville High School recently won science fair at the school-based level and moved on to Fairfax County Regional Science & Engineering Fair that took place on March 15-17, 2013. Her project involved analysis of Space Weather forecasts from http://swxcontest.gmu.edu/

Student project: John Lear

John Lear is working with John Mariska measuring the variability of the Hinode EUV Imaging Spectrometer solar coordinate system as a function of time by comparing images taken with EIS and the AIA experiment on the Solar Dynamics Observatory.

  • Student project: Tran Tran

    Student: Tran Tran
    Sponsor: OSCAR program, won a $1,000. grant to do the work
    Project: Determine the absolute velocity of hot gases in coronal loops.
    Faculty Mentor: Art Poland

  • Rebekah Evans Minnel, PhD Dissertation

    Coronal Heating by Surface Alfven Wave Damping

    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.

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