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Session 70 - Solar Flares and Ejections.
Display session, Thursday, June 13
We have previously reported that large, outstandingly-bright coronal loops within an active region or stemming from an active region have one end rooted around a magnetic island of included polarity that is itself a site of locally enhanced coronal heating (X-ray bright point) [Porter et al 1996, in Proceedings of the Yohkoh Solar/Stellar IAU Symposium, ed. Y. Uchida, T. Kosugi, H.S. Hudson (Kluwer: Dordrecht), in press]. This suggests that exceptional magnetic structure in and around the magnetic island fosters magnetic activity, such as microflaring, that results in the enhanced coronal heating in both the compact core field around the island and in the body of large loops that extend from this site. We have also reported that enhanced coronal heating in active regions goes hand-in-hand with strong magnetic shear in the core magnetic fields along polarity neutral lines (Falconer et al 1995, BAAS, 27, 976). Here, by combining MSFC vector magnetograms with an NSO full-disk magnetogram and Yohkoh SXT coronal images, we examine the incidence of sheared core fields, enhanced coronal heating, and microflaring in two active regions having several good examples of enhanced extended coronal loops. It appears that the localized microflaring activity in sheared core fields is basically similar whether the core field is on the neutral line around an island of included polarity or on the main neutral line of an entire bipolar active region. This suggests that the enhanced coronal heating in an extended loop stemming from near a polarity inversion line requires a special field configuration at its foot to plug it into the activity at the neutral line, rather than a different kind of activity in the core field on the neutral line. We also examine whether the waxing and waning of the coronal brightness of extended loops shows any correlation with the vigor or frequency of microflaring at the feet. This research was supported by the Solar Physics Branch of NASA's Office of Space Science.
Program listing for Thursday