Evolution of a Solar Active Region and Flare Productivity

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Session 68 -- Solar Activity
Oral presentation, Thursday, January 13, 2:15-3:45, Salons A/B Room (Crystal City Marriott)

[68.07] Evolution of a Solar Active Region and Flare Productivity

M.R. Kundu (U. Maryland), K. Shibasaki, S. Enome (Nobeyama), N. Nitta and M. Bruner (Lockheed)

We have studied the evolution of an active region (AR 7515) in terms of flare productivity. This region appeared on the east limb on May 23, 1993 and continued its onward march across the disk. We followed its evolution until June 2. This region produced many small flares. We studied the topology, both magnetic and structural of the flaring region as observed at 17 GHz by the Nobeyama radio Heliograph (NRH) with a spatial resolution of 10 arcsec and the Yohkoh SXT which has a spatial resolution of 2.5 arcsec. Among other things, we find: (i) Frequently a flare starts with the appearance of a new region/loop which interacts with a pre-existing loop; this interaction acta as a flare trigger. (ii) There appear to exist multiple sets of interacting loops in the same active region. Different bursts on the same day seem to come from diffrent sets of interacting loops. (iii) Sometimes two or more sets of interacting loops can activate at the same time, giving rise to different peaks in the same burst. In the decay phase of some bursts there may appear a new or reactivated region/loop which becomes the source of new burst emission. (iv) A simple spiky burst in general originates from a narrow region and by implication from a compact set of interacting loops.

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