The Response of African Equatorial Ionosphere to Major/Intense Geomagnetic Storms during the Period: 2011–2012

This study presents the response of African equatorial ionosphere to major/intense geomagnetic storms that occurred during 2011-2012. The data for the study were obtained from four African GNSS stations, namely; Ilorin (8.48^oN, 4.54^oE, and mag lat: 1.83^oS) [Nigeria], Nsukka (6.84^oN, 7.37^oE, and mag lat: 2.94^oS), [Nigeria], Dakar (14.75^oN, 17.45^oW, mag. lat: 5.88^oN) [Senegal] and Addis Ababa (9.03^oN, 38.77^oW, mag. lat: 0.18^oN) [Ethiopia]. The stations are located at the magnetic equator and the inner flank of the equatorial ionization anomaly. We characterized GNSS scintillation (S4 index) and total electron content (TEC) data alongside the days of major geomagnetic storms that occurred during the period of 2011-2012. For the TEC data, the occurrence of geomagnetic storms influenced TEC measurement significantly at the four stations. However, the impacts of geomagnetic storms occurrences on scintillations were not very noticeable at the stations, most especially at Addis Ababa. In fact, it appears that scintillation occurrences were inhibited during geomagnetic storm occurrences at the magnetic equator. Generally, the ionospheric parameters (TEC and S4) recorded the highest at Dakar, and the least at Addis Ababa. Seasonally, ionospheric TEC and scintillations recorded highest occurrences during equinoxes, and the least during June solstice. These results could support the development of adaptable ionospheric models during intervals of space weather events for equatorial Africa, and could also be of benefit to GNSS service providers and designers, with a view to providing robust services for GNSS user community in Africa.