Emergence of twisted magnetic-flux bundles and flare activity in a large active region, NOAA 4201

To reveal what is the key agent for strong flare activity, we studied the e volution of a large sunspot group, NOAA 4201, and its flare activity. We an alyzed high-resolution H alpha images obtained with the Domeless Solar Tele scope at Hida Observatory, and Kitt Peak full disk magnetograms. We examine d the sunspot proper motions and evolutionary changes of H alpha fine struc tures and magnetic fields in this active region, and constructed a schemati c model of emerging twisted magnetic-flux bundles. We also found that the o ccurrence of high flare activity was restricted to the rapidly emerging reg ion of the twisted flux bundle. This fact suggests that the emergence of a twisted emerging flux bundle should be the key to high flare productivity o f the sunspot group.