A Large Spot Group of Active Region YR80-575

The YR80-575 (Boulder 2779) active region, S_l2 L₉₇ CMP 11.7 November 1980, was observed in sequence at Yunnan Observatory from Nov. 5 to 17 in SMY.During its passage across the solar disc the flares occurred frequently and a part of them was accompanied by strong x-ray and SWF events, including an X9/3B flare at 0542UT on 6th Nov., the strongest X x-ray event scince July 11, 1978.One of the morphological characters of this region appeared as the spot group which maximum area was the largest one in Cycle 21^*. This spot group was the regressive one of the old active region (YR 80-529) and some new spots emerged around the old spots, then they became a very complex FKC-group with a large area, strong magnetic gradient and δ-configuration. The average magnetic field intensity of the total group was about 2000 gauss and the maximum magnetic field intensity measured in some main spots was 3300 gauss.The intense motion, rotation, separation, combination and interaction among the spots were observed in this complex spot group. It was found that an anormal light bridge formed in the old main spot when the two umbrae merged into one instead of the opposite case, i. e., one umbra split into two.