Fall 2015 Space Science Seminars

11 AM – noon, Room 242 of Planetary Hall unless otherwise noted.

December 1st

James Leake

NRL

November 17th

11 AM – noon, Room 242 of Planetary Hall

Jia Yue

Lower-Upper Atmosphere Cooling — from Milliseconds to Decades

November 11th

Erdal Yiğit and John Lear

Recent MAVEN-Mars results

August 11

Temporal evolution of the horizontal motion, buoyant velocity and magnetic field of an emerging active region

Chia-Hsien Lin

Graduate Institute of Space Science, National Central University, Chung-Li, Taoyuan, Taiwan

Abstract: We examined the emerging process of NOAA AR11645 from the
earliest detection of magnetic flux in the region. The observed horizontal
motion of the emerging flux is compared with its average magnetic field
strength and the vertical motion derived from the magnetic buoyancy theory.
The magnitude of the theoretically derived thick-tube buoyant velocity of
the inclined fields is comparable to that of the observed separation velocity
of two polarities. The thin-tube approximation results in an unreasonably
high buoyant velocity, indicating that the approximation is inappropriate
for emerging active regions. While the observed horizontal motion is not
found to directly correlate with either the magnetic field strength or the
derived buoyant velocities, the separation velocity of two poles, the temporal
derivative of the average magnetic field strength, and the percentage of the
inclined fields all show a similar decreasing profile. The results of this study
imply that the assumption that the emerging active region is the cross section
of a rising flux tube whose structure can be considered rigid as it moves across
the solar surface should be taken with caution.

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