The flares associated with the abnormal rotation rates of the bipolar sunspots: Reconnection probably below the surface

Abstract

We use the observations of Kodaikanal observatory white light pictures to study the association between the rotation rates of the bipolar sunspots and triggering of the flares. For the years 1969-1974, we compute daily rotation rates of the leading and the following spots of the bipolar sunspot groups during their life span. We find that either leading or following or both of the bipolar spot groups which have abnormal rotation rates during the course of their evolution are strongly associated with the occurrence of flares in the later stage of their life span. Other important findings are: (i) the abnormal rotation rates and the flares occur during the 50-80% of their life span of the spot group and, (ii) abnormal rotation rate of about 2deg/day is required for triggering the flares. The strong relation between the occurrence of abnormal rotation rates of the sunspot groups and the occurrence of the flares enabled us to estimate the probable region of depth of reconnection below the solar surface.