34th Solar Physics Division Meeting, June 2003
Session 15 Flares and Microflares I
Oral, Wednesday, June 18, 2003, 1:30-3:30pm, Auditorium

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[15.08] Rapid Changes in the Longitudinal Magnetic Field Associated with the July 23, 2002 \gamma-ray Flare

V. B. Yurchyshyn, H. Wang, V. I. Abramenko, T. J. Spirock (Big Bear Solar Observatory), S. Krucker (Space Sciences Lab, UC, Berkeley)

In this paper we analyze and discuss rapid changes of the magnetic field associated with the July 23, 2002 \gamma-ray flare. MDI magnetic flux profiles and BBSO vector magnetograms showed that immediately after the flare the leading polarity had increased by 2\times1020Mx, while the following polarity decreased only by 1\times1020Mx. The observed changes were permanent and not caused by variations in seeing or changes in the line profile, which we used to measure the magnetic field. In this active region we distinguish two separate locations, which show the most dramatic changes in the magnetic field. The first location showed an increase in the magnetic field strength and a new penumbra area and it was associated with emergence of new magnetic flux. At the second location the position of the neutral line had changed and it coincided with the footpoints of a rapidly growing post-flare loop system. Linear force-free field simulations showed that the re-orientation of the magnetic field during the flare was capable of producing the observed changes in the total magnetic flux. We also discuss a possible magnetic configuration responsible for the flare. This work was supported in part by NSF ATM-0086999 and ATM-0205157 and under NASA NAG5-10910 NAG5-12782 grants.

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Bulletin of the American Astronomical Society, 35 #3
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