In this pater, the morphology, ares, sunspot number and produced different events of a gyrotion sunspot group (AR6818, AR6850, AR6891, AR6932)(Boulder) during visible solar disk in 1991 are statistically analysed and discussed.

• 本文对1991年中的一个回转群Boulder编号6818,6850,6891,6932活动区(AR6818,AR6850,AR6891,AR6932)的形态,面积,黑子数及在可见日面期间所产生的各种事件进行统计分析及讨论。