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Abstract:
We present a comparative study of the major and minor SSWs that have occurred in the Northern Hemisphere (NH) and Southern Hemisphere (SH) over the past four decades (1981–2020) from a statistical perspective. We have investigated the frequency and timing of the occurrence of major and minor SSWsduring the specified period. For the Arctic SSWs, a correlation is observed between the timing of the earliest minor SSWs and final events, having different correlation coefficients in all four decades, with minimum correlation during the decade 2001–2010, which includes the extended solar minima. Our work also presents an extensive study of Arctic and Antarctic SSW events of the last 18 winters based on ERA5 and MERRA2 reanalysis data. The stratospheric parameters have been found to show different behaviors depending on the number of SSW events in a particular winter. Finally, we have studied the atmospheric and ionospheric response to major and minor SSWs. For the Arctic SSWs, ionospheric parameters have been studied over three stations, namely Okinawa (26.21◦N, 127.68◦E), Yamagawa (35.45◦N, 133.62◦E), and Wakkanai (45.16◦N, 141.75◦E). Like the stratospheric parameters, ionospheric parameters are not found to be much dependent on the number of SSWs in the winter, but they are found to vary from event to event. For Antarctic SSWs, we examined the ionospheric behavior at two conjugate locations, Okinawa and Darwin (12.46◦S, 130.84◦E). Although ionospheric disturbances are more pronounced during major SSWs, some severe minor events also have notable ionospheric impacts, just like the major SSW.
