34th Solar Physics Division Meeting, June 2003
Session 16 Flares and Microflares II
Poster, Wednesday, June 18, 2003, 3:30-5:00pm, Mezzanine

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[16.19] Rapid Penumbral Decay in Active Region NOAA~9026 Associated with Two X-Class Flares

N. Deng, C. Liu, G. Yang, H. Wang, C. Denker (NJIT/CFSR/BBSO)

In recent studies, we found that the longitudinal magnetic field changes drastically during energetic M- and X-class flares. In this poster, we show an example of rapid penumbral decay associated with two X1.1/X2.3 flares in active region NOAA~9026 on 2000 June 6. From about 08:00~UT to 13:30~UT, several C-class and one M-class flares occurred in the active region. An X1.1 flare started at 13:00~UT and reached its maximum at 13:39~UT, which was followed by another M7.1 flare at 13:56~UT. This flare reached its maximum at around 14:01~UT and decayed quickly and ended at 14:11~UT. The largest event was an X2.3 flare starting at 14:58~UT. It reached its peak at around 15:25~UT and since then decayed slowly. The penumbra in two distinct regions partially disappeared as a result of the X-class flares. This event also produced a type II radio burst (1189~km/s), a type IV radio burst, an 11-degree long filament eruption, and full-halo coronal mass ejection (CME). Even though the penumbral decay happened in a \delta-sunspot, our observations will provide guidance for subsequent studies employing two-dimensional spectro-polarimetry and image reconstruction, and for models to understand active region evolution and solar activity.

This work was supported by NSF under grant ATM 00-86999, ATM 00-76602, and ATM 02-36945, and by NASA under grant NAG 5-9682.

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Bulletin of the American Astronomical Society, 35 #3
© 2003. The American Astronomical Soceity.