Solar radio bursts, proton events and geomagnetic activity

The relationships between type 2, type 4, microwave bursts and geomagnetic activity have been studied using data from various observatories compiled in the Solar-Geophysical Data over the period 1968-1982. It is found that type 2 bursts follow the trend of solar activity in general, more bursts occurring during periods of high solar activity. A similar trend is also seen with type 4 bursts but their occurrence frequency is smaller than that of type 2 bursts. Superposed epoch analysis of geomagnetic activity index Ap before and after the events shows no dependence on type 2 bursts but the relationship with Ap improves following type 2/4 bursts and a still better improvement is observed with type 2 bursts associated with moving type 4 events. The position of type 2 burst on the solar disk does not seem to affect the Ap values significantly. Similar analysis carried out on the days of occurrence of solar proton events during 1970 to 1979 showed that an enhancement in Ap index on the second/third day is clearly seen in some years but not in all. But on the average, Ap shows significant increase if we consider longer periods, i.e., 5 to 10 year.