Ionospheric Response to the Strong Geomagnetic Storm of January 2025 at African Equatorial Stations

Total electron content (TEC) measurements from two International Global Navigation Satellite System (GNSS) Service (IGS) stations were utilised to investigate how the equatorial ionosphere responded to the strong geomagnetic storm of 1 January, 2025. The stations and their respective geographical coordinates are Libreville, Gabon (0.354° N, 9.672° E) and Mbarara, Uganda (0.601° S, 30.738° E), respectively representing the western and eastern parts of the African equatorial sector. In the storm’s main phase, no significant ionospheric perturbation was observed at either station. However, during the recovery phase, Libreville exhibited exclusively a nighttime negative storm phase, while Mbarara exhibited both positive and negative phases, indicating marked longitudinal asymmetries in ionospheric response. These differences could be associated with the modulation of F-region dynamics by local electrodynamic processes, such as disturbance dynamo and prompt penetration electric fields, and storm-induced thermospheric composition changes