Rapid Penumbral Decay Following Three X-Class Flares |
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Haimin Wang Submitted: 2003-11-10 12:35
We show strong evidence that penumbral segments decayed rapidly and permanently right after three X-class flares. Two of the three events occurred very recently in solar active region NOAA~10486, an X17 flare on 2003 October~28 and an X10 flare on 2003 October~29, 2003. The third X2.3 flare was observed in solar active region NOAA~9026 on 2000 June~6. The locations of penumbral decay
are closely related to hard X-ray flare kernels or coincide with the central region of flare ribbons seen in extra-ultraviolet (EUV) images obtained by the
Transition Region and Coronal Explorer (TRACE). We present difference images high-lighting the rapid changes between pre- and post-flare states of flaring
active region, which show distinct decaying penumbral segments and neighboring umbral cores becoming darker. This indicates that magnetic fields change from a
highly inclined to an almost vertical configuration within approximately one hour after the flares, i.e., part of the penumbral magnetic field is converted into umbral fields.
Authors: Haimin Wang, Cheng Liu, Jiong Qiu, Na Deng, Phil Goode and Carsten Denker
Projects: RHESSI,TRACE
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Publication Status: Ap.J. Letters (submitted)
Last Modified: 2003-11-18 14:18
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