Asymmetry of distribution of Hα flares on the solar disk in the 21st cycle

Abstract

The North-South and East-West asymmetries of distribution of Hα flare numbers on the solar disk in the 21st cycle of the solar activity are studied. It is shown that the mean number of flares on the eastern half of the solar disk is, on average, by 2.7% more than that of the western one, and there is only a slight difference between the numbers of northern and southern flares. However, more flares occurred in the northern hemisphere at the beginning of the cycle, while more were at the end of the cycle in the southern one. It is shown that North-South asymmetry has a period of 540 days, and the East-West asymmetry is characterized by an annual period. Also, the East-West asymmetry is explained by the planet effect on the solar activity.