Hemispherically and Longitudinally Asymmetric Ionospheric Response to the 23–24 March 2023 Geomagnetic Disturbances at Three Pairs of Conjugate Stations

Abstract

The effects of the 23–24 March 2023 geomagnetic storm in the magnetically conjugate low-latitude ionosphere-thermosphere along the 72°E ± 5°, 95°E ± 5° and 130°E ± 5° sectors are presented. The Total Electron Content (TEC)/NmF2 data from ground stations as well as satellite data, and model simulations are utilized to investigate the hemispheric and longitudinal variations. For the India-East Asia region, the most prominent TEC variations manifested only on 24th March. In all the three sectors, the northern VTEC/NmF2 showed a stronger negative effect with maximum depletion over the low-middle latitude station Dibrugarh (∼75–80%). The TEC map generated from the South–East Asia low latitude network suggested an underdeveloped EIA along 100°E on 24th March. The vertical electron density profiles estimated from COSMIC RO confirmed the hemispheric and longitudinal asymmetry of the F2 layer density. The conjugate hemisphere F2 layer height variation was indicative of equatorward winds in the Southern Hemisphere and poleward winds in the Northern Hemisphere. SWARM B on 24th March not only recorded the hemispheric asymmetry in the topside but also indicated equatorward winds in the southern hemisphere. The Thermosphere-Ionosphere-Electrodynamics General Circulation Model and WAM IPE models underestimated, whereas the IRI overestimated the low latitude storm time TEC. The negative effect can be attributed to the Disturbance Dynamo Electric Field, whereas the asymmetric equatorward expansion of the thermospheric composition perturbation and winds may have led to the hemispheric asymmetry of the storm response. Therefore, a conjugate ionospheric response in three close-by sectors suggests a possible role of inter-hemispheric meridional winds in equinoctial conditions for the asymmetric effects.