HR: 1330h
AN: SH42B-0521    [PDF]
TI: On Flux Rope in the 1997 May 12 Event
AU: * Liu, Y
EM: yliu@quake.stanford.edu
AF: HEPL, Stanford University, 455 Via Palou, Stanford, CA 94305 United States
AU: Forbes, T G
AF: Institute for the Study of Earth, Ocean, and Space, University of New Hampshire, University of New Hampshire, Durham, NH 03824 United States
AB: The solar source of this event was reported to be an C1.3/1N flare with a duration of more than 8 hours, occurring at 04:42 UT on 12 May 1997 in the active region AR8038 at N21W08, which was the only active region in solar disk. The magnetic configuration of this active region is very simple -- a dominant leader sunspot with positive polarity surrounded by weak negative magnetic field patches. Associated with this flare were eruption of a filament and a complete halo CME with a speed of \( 250 km\dot s^{-1} \) (Plunkett, {\it et al.}, 1999). {\it SOHO} also observed double dimmings and EIT wave (Thompson, {\it et al.}, 1999). This flare appears to be a classic two-ribbon flare: With eruption of the filament, two bright ribbons showed up and moved apart, seen in H$\alpha$ observation; sigmoidal bright patterns shown in {\it YOHKOH/SXT} and {\it SOHO/EIT} images became post-flare arcades; and magnetic shear computed from observed vector magnetic field significantly decreased. These observations provide an opportunity for us to investigate the possible flux rope in this event, as illuminated in the two-ribbon flare model. We took three approaches to estimate the properties of the flux rope in this event. We found that the twist from these methods is strikingly different. We will discuss possible errors in our computation. This research was supported by NASA under contract NAS5-30386, MURIs of UC Berkeley and Michigan University, and the CISM of Boston University. SOHO is a joint project between the ESA and NASA.
DE: 7500 SOLAR PHYSICS, ASTROPHYSICS, AND ASTRONOMY
DE: 7513 Coronal mass ejections
DE: 7524 Magnetic fields
SC: SPA - Solar and Heliospheric Physics [SH]
MN: 2003 Fall Meeting