Response of Ionospheric Parameters at Low‐Latitude and Mid‐Latitude Stations to Geomagnetic Storms of March and April 2025

This study investigates ionospheric responses to geomagnetic storms of 21–24 March and 15–17 April 2025 using GNSS‐derived total electron content (TEC), magnetometer observations, and thermospheric O/N 2 measurements at low and mid‐latitudes across the Northern Hemisphere of the Europe–Africa sector. The March storm reached a SYM‐H minimum of −72 nT, driven by a CME with a brief southward IMF‐Bz interval followed by a high‐speed stream (HSS). Low‐latitude African stations recorded night‐time TEC enhancements of +85% to +168%, attributed to prompt penetration electric fields (PPEFs) driving night‐time upward E × B plasma transport, while mid‐latitude European stations exhibited mixed deviations. Elevated daytime O/N 2 ratios indicate reduced molecular recombination in the F region during the daytime, consistent with positive daytime ionospheric responses at low latitudes. The April storm reached a SYM‐H minimum of −150 nT, from a compound CME–HSS interaction sustaining southward IMF‐Bz conditions. During 16–17 April, mid‐latitude European stations experienced TEC reductions of −52% to −69% in the main phase, while low‐latitude stations displayed alternating responses. O/N 2 ratios decreased to 0.6–0.8 across the sector, consistent with enhanced molecular recombination and negative ionospheric responses at mid‐latitudes. Magnetometer observations revealed storm‐time perturbations after sudden commencement, consistent with prompt penetration electric fields, followed by latitudinal disturbances during late main and recovery phases. Magnetic signatures for disturbed ionospheric currents Diono, negative at low latitudes and positive at mid‐latitudes, agree with the polarity predicted by the disturbance dynamo model of Blanc and Richmond (1980, https://doi.org/10.1029/ja085ia04p01669 ). These results demonstrate how storm evolution and solar‐wind forcing shape ionospheric variability within the Europe–Africa sector.