Total Electron Content Variability in the African Ionosphere Observed during Ascending and Decaying Geomagnetic Storms

• Published in: Geomagnetism and Aeronomy 2023-12, Vol.63 (6), p.839-853
• Main Authors: Anoruo, Chukwuma Moses, Okeke, Francisca Nneka, Okpala, Kingsley Chukwudi
• Format: Article
• Language: English
• Subjects: Anomalies; Earth and Environmental Science; Earth Sciences; Electric fields; Equatorial ionization anomaly; Geomagnetic storms; Geomagnetism; Geophysics/Geodesy; Global navigation satellite system; Ionization; Ionosphere; Ionospheric electron content; Ionospheric plasma; Latitude; Magnetic fields; Magnetic storms; Navigation satellites; Navigation systems; Phases; Recovery; Satellites; Solar activity; Solar activity cycles; Storms; Total Electron Content; Wind speed
• ISSN: 0016-7932; 1555-645X; 0016-7940
• DOI: 10.1134/S001679322360042X

The geomagnetic storms of October 1, 2012, and May 28, 2017, of the mid- and equatorial-latitude ionosphere responses of the African sector at cycle 24 solar ascending and descending levels are presented. The relative total electron content (rTEC) anomalies at the initial commencement until recovery phases of storms present interesting results. We employed a 15-day sliding average window to study rTEC using 7 (Global Navigation Satellite Systems) GNSS stations from the Africa Geodetic Reference Frame (AFREF) to characterize both storm ionospheric phases over the sector. The recovery phase of both storms lasted 17 h for October 1 and 14 h for May 28 with IMF Bz < 0 when the solar plasma wind speed recorded values of 353 km/s and 336 km/s, respectively. The results showed a significant equatorial latitude response of the ionosphere during both the main and recovery phases of storms that occurred at different solar activity cycles, where prestorm TEC changes occurred during the daytime. Again, positive storms observed during the prestorm events place less emphasis on the solar activity cycle mostly observed at the equatorial latitude. In addition, the magnetic field lines are shaped by the injection of a prompt penetration electric field (PPEF) that prompts prestorm rTEC enhancements, where the phenomenon of the equatorial ionization anomaly (EIA) governs the midlatitude Africa ionospheric plasma distribution based on gradients and is more pronounced in the poststorm effect.