Substorm related CNA near equatorward boundary of the auroral oval in relation to interplanetary conditions

Abstract

Cosmic noise absorption (CNA) at high latitudes is a typical manifestation of enhanced precipitation of energetic charged particles during the course of a magnetospheric substorm. Present analysis demonstrates the energetic particles precipitate to the high latitude ionosphere during substorms, affecting upper and lower regions of the ionosphere simultaneously. Previous studies have reported that intense and short-lived CNA events associated with substorms are mostly observed in the midnight sector of the auroral oval. In the current study, we have examined such type of CNA events predominantly occurring during 0000–0600 UT (2300–0500 MLT) at an Indian Antarctic station Maitri (corrected geomagnetic (CGM) coordinates 62.59°S, 53.59°E), which is located at the equatorward edge of the auroral oval. Absorption events related to isolated substorm and storm-time substorms exhibit distinct features in terms of their intensity and extent in latitude and longitude. Our study suggests that the maximum intensity of CNAs depends on the interplanetary conditions, such as, the solar wind speed, southward component of IMF Bz, and duskward component of IEF Ey. Moreover, the role of duskward component of IEF Ey is more noteworthy than other interplanetary parameters.