Effect of severe geomagnetic storm on ionospheric TEC at two longitude regions

Abstract

In this study, we investigated the responses of the ionosphere during a severe geomagnetic storm at six stations at two distinct latitudes around approximately (75 ± 5) ° E (IISC, POL2, and DGAR) and (145 ± 5) ° E (GUUG, MTKA, and LAE1). In order to investigate the impact of severe geomagnetic storms with Dst indices of− 404.14 nT and− 437.28 nT, respectively, that occurred on May 10 and 11, 2024, we used Global Positioning System (GPS) based total electron density (TEC) data and O/N₂ ratio plot downloaded from the TIMED/GUVI website. The TEC value was impacted by this geomagnetic storm, positively and negatively at both latitudes. The effect is mainly due to the combined action of prompt penetration electric field (PPEF), disturbance dynamo electric field (DDEF) and traveling ionospheric disturbances (TIDs). The O/N₂ ratio played a crucial role in deciding positive and negative effect on TEC during geomagnetic storm which is evident by the results obtained from two latitudes on same longitude. On May 11, 2024, the combined impact of DDEF and storm-induced traveling ionospheric disturbances (TIDs) may have caused an increase in TEC. By longitudinal comparison of geomagnetic storm effect, we found that the two stations on the nearly same latitude (~ 6.5 ° S) show different type of variation in TEC and O/N₂ ratio. On commencement of storm (May 10 and 11) the effect was different at different stations. We observed longitudinal and latitudinal variations both. The increment in TEC at LAE1 is a greater amount compared to that at DGAR. At IISC and GUUG, we observe that during the main phase of the storm on 11th May, the effect was positive, but during the recovery phase, it became negative on the same day at both stations. There was a negative effect at both stations, MTKA and POL2, in different amounts. On 11 May, this effect at MTKA was less in comparison to POL2, and on 12th May the effect at MTKA was very large in comparison to that at POL2.