NOAA 8210 produced several M and X class flares with eruptive events caused strong geomagnetic activity. The M7 flare of 29 April was observed at Mees Solar Observatory beginning during the rise phase.
The magnetic neutral line spirals around the large spot and divides a small delta spot to the southwest. The transverse field azimuth has large tangential discontinuity ("shear") in the delta spot.
The H-alpha imaging spectra show the filament which lay along the neutral line erupting with vector velocities > 150 km per second. The flare ribbon lies on the negative polarity of the delta spot, but lies on the positive polarity farther along the neutral line, demonstrating that the energized field lines are still sheared. The spectrum shows blue-shifted absorption in the erupting filament at the north (top) and the broad redshifted emission in the beam-heated footpoint at the south (bottom).
Images are:
Barry LaBonte
Institute for Astronomy
University of Hawaii
Last modified: Thu Jan 27 14:36:57 HST 2000