A major solar flare in a small δ-type active region

A small δ-type active region was observed on September 14–18, 2000 at Ganyu Station of the Purple Mountain Observatory. It developed rapidly during its passage through solar disk and there was a stereo-typed spiral filament near the magnetic inversion line on 15–17th, Sept. Its magnetic axis made an angle 85° to the equator. On Sept. 16 it produced a major flare, 3B importance, having more intense geophysical effects. Using the vector-magnetograms the distribution of magnetic field lines was deduced. The analysis of QSL stereo-map made a discovery that there is a null or separator about such spiral filament which can be used to explain the formation of this major flare and intense mass ejection.