An Analysis on the Strongest Active Regions of Solar Cycle 21st

A total o f 3986 active regions are recorded during the 21st Solar Cycle. We define 16(e.g. AR3804, AR4474) of the active regions as the strongest active regions in terms of 4 indicies-sunspo tarea, index of the X-Ray flares, 10.7cm radio flux and proton event index. Compared with 22nd Solar Cycle we found that both have the characteristics: for the 21st Solar Cycle, the active regions dist ribute cent rally in the 4 time periods but for the 22nd in 2 periods; for the 5 "hot spots" only those lieat the neighboring of 85° lati tude in the southern hemi sphere are similar to one of the 3 hot spots of the 22nd Solar Cycle. Generally, the level of activity in the 21st Solar Cycle is lower than that in the 22nd Solar Cycle, especially in the respect of X-ray and proton events.