Dynamic Processes Associated With Prominent Ionospheric Variations in a Narrow Longitudinal Zone Near the EIA Crest Region as Revealed by ICON Satellite and Ground Beidou Receiver Observations Over South Asia

Abstract

Neutral winds and plasma motions from the Ionospheric Connection Explorer mission were used to investigate dynamic processes associated with large regional total electron content (TEC) differences in a narrow longitudinal zone exceeding ∼45 TECU obtained from dense Beidou geostationary receivers at low latitudes over South Asia. The TEC east‒west asymmetry was defined to quantify this difference, which exceeded ∼5 TECU per 1° longitude distance and occurred around the equatorial ionization anomaly (EIA) crest on 31 March 2021 under geomagnetically quiescent conditions. Moreover, the magnetic meridional ion velocity exhibited a large longitude difference around the EIA crest during periods with strong ionospheric east‒west asymmetry. Furthermore, the longitude difference variation was consistent with the TEC east‒west asymmetry variation during 11–21 March 2020 and 27 March–4 April 2021. No significant correlations between TEC east‒west asymmetry and longitude differences under conditions with neutral winds and magnetic zonal ion drifts were observed in either case. The different vertical plasma drifts could contribute to ionospheric changes with a zonal range of a few hundred kilometers.