Total Electron Content Variability in Response to Solar Flares and a Geomagnetic Storm Over East Africa during May 8–15, 2024

Abstract

This study investigates the ionospheric response over the East Africa region during solar flares and a geomagnetic storm from 8–15 May 2024. During this period, 12 X-class solar flares and one extreme geomagnetic storm occurred, causing pronounced variability in total electron content (TEC). X-ray flux measurements from the Extreme Ultraviolet and X-ray Irradiance Sensors (EXIS) on board the Geostationary Operational Environmental Satellites (GOES) are analyzed to detect solar flares. TEC derived from four GNSS receiver stations and the IRI-2020 model, O/N₂ ratio maps, and an ionospheric electric fields model are used to identify ionospheric variation owing to the space weather events. The X-class flares prior to May 11 produced immediate TEC enhancements of up to +15 TECU relative to quiet day levels, consistent with sudden ionospheric disturbances. In contrast, the geomagnetic storm on May 10–11 induced both positive and negative storm phases, with TEC deviations ranging from –31.46 to +33.13 TECU. During the main phase of the geomagnetic storm, at the ADIS station, TEC increased by +10.8 TECU and then decreased by –8 TECU. In the recovery phase, it increased to +31 TECU. At the DJIG station during the main phase, TEC decreased by –16.1 TECU, followed by a significant positive enhancement reaching +30.5 TECU on May 12th. Similarly, the MAL2 station recorded a minimum negative TEC deviation of –16.6 TECU during the main phase, with a notable maximum positive deviation of +33.03 TECU also occurring on May 12th. For the MBAR station, the main storm phase on May 10th showed a minimum negative TEC deviation of –15.94 TECU, and a maximum positive deviation of +33.13 TECU was observed on May 12th. We have used correlation coefficients (\(r\)), Percentage Root-Mean Square Error (PRMSE) and root mean square errors (RMSE) to examine the variation of the IRI-2020 TEC from the GPS TEC during the storm. The results show that the model performed best at the ADIS station, with the highest \(r\) (0.93) and the lowest RMSE (13.33) and PRMSE (28.31%). These study enhance our understanding of solar flare and geomagnetic storm impacts in equatorial and low latitude regions, which is crucial for improving space weather forecasting and mitigating risks.