Investigation of Subauroral Ionosphere under Disturbed Geomagnetic Conditions during the High Solar Activity Year 2012 at Maitri, Antarcitica

Abstract

The present study investigates the subauroral ionospheric response to geomagnetically disturbed conditions across different seasons of 2012, using Total electron content (TEC) and S4 index data derived from a Global Positioning System (GPS) receiver installed at the Indian Antarctic station Maitri (geographic coordinates: 70.76° S, 11.74° E). TEC and S4-index measurements for January, March, and June 2012 were analysed alongside the corresponding Auroral Electrojet (AE) index and the interplanetary magnetic field (IMF) Bz component to assess seasonal variability in ionospheric behaviour. The results reveal that the subauroral ionosphere exhibits a negative response (i.e., TEC depletion) during periods of southward IMF Bz orientation, whereas a positive response is generally observed during northward IMF Bz, particularly during the summer and equinoctial periods. In contrast, this trend appears to reverse during the winter season. The observed negative ionospheric responses are attributed to a combination of equatorward plasma transport and thermospheric compositional changes. Additionally, poleward compression of the auroral oval and enhanced molecular precipitation are believed to contribute to these depletions. Furthermore, the study examines the occurrence characteristics of amplitude scintillations under disturbed geomagnetic conditions. It is observed that the intensity of amplitude scintillation during the winter (polar night) is significantly higher compared to that during summer and equinox periods, suggesting enhanced small-scale ionospheric irregularities under such conditions.