Equatorial F region irregularities during MiniMax and the onset conditions in the Indian sector

The strange behavior of the ongoing solar cycle has attracted worldwide attention of the ionospheric community in an effort to understand the impact of the solar activity on the ionosphere in general and ionospheric plasma irregularities in particular. Unexpected results obtained during the prolonged deep solar minimum during 2008-2009 have already been witnessed. Although it is known that characteristics and occurrence of equatorial F region irregularities vary with solar activity, the effect of relatively low level of solar flux during the present maxima on the occurrence and characteristics of F region irregularities has yet to be known. In this paper, we present results on F region plasma irregularities based on extensive radar observations made during the MiniMax of the solar cycle 23/24. These observations were made using the newly established Gadanki Ionospheric Radar Interferometer (GIRI) in the scanning mode providing zonal distribution and drifts of the plasma irregularities. The onset location and ionospheric background conditions have been studied using the scanning capability of GIRI, collocated digisonde and C/NOFS satellite observations. The study also includes the role of the solar terminator and sporadic E conditions. Results obtained during the MiniMax are finally compared with those observed during the similar solar activity condition of the previous solar cycle.