Solar Physics Division Meeting 2000, June 19-22
Session 2. Corona, Solar Wind, Flares, CMEs, Solar-stellar, Instrumentation, Other
Display, Chair: J. Krall, Monday-Thursday, June 19, 2000, 8:00am-6:00pm, Forum Ballroom

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[2.67] A Rapid Magnetic Connectivity Change Observed Before a Filament Eruption

Jung-Hoon Kim, H.S. Yun, Sangwoo Lee (SNU), J. Chae, P.R. Goode (BBSO)

It has been a mystery what causes a solar prominence eruption. To get an insight on this problem, we observed an active region filament eruption in H\alpha lines (line center, ± 0.5 {Å}) and longitudinal magnetograms at Big Bear Solar Observatory. The cadence is about 1 minute each for H\alpha and magnetogram. During 8 hours of observing run, we covered complete phases of the filament eruption and an associated two-ribbon flare. From H\alpha movies, we found a rapid connectivity change in a filament thread before its eruption. The thread was initially highly curved. It suddenly became straightened due to the rotation of its end. The duration of change was about 30 minutes and the rotated thread swept 100{\arcsec}\times50{\arcsec} area on the solar surface. After this connectivity change, the filament body split into two parts, one part erupted, and the two-ribbon flare occurred. Being associated with the connectivity change, transverse mass motion of about 50 km/s was observed in H\alpha along the newly connected field lines, and a cancelling magnetic feature was observed in the vicinity where the connectivity changed. Flux cancellation began before the connectivity change, and continued while the connectivity change proceeded. Within 2 hours, the flux decreased by the amount of about 2.0\times 1020 Mx. These observational results clearly give direct evidence that magnetic reconnection takes place prior to eruption. This reconnection is distinct from the post-eruption reconnection which is believed to lead to the two-ribbon flare.

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