Response of GPS-TEC in the African equatorial region to the two recent St. Patrick's day storms
Ikubanni, SO and Adebiyi, SJ and Adebesin, BO and Dopamu, KO and Joshua, BW and Bolaji, OS and Adekoya, BJ, Response of GPS-TEC in the African equatorial region to the two recent St. Patrick's day storms, International Journal of Civil Engineering and Technology, 9, (10) pp. 1773-1790. ISSN 0976-6308 (2018) [Refereed Article]
The 2015 St. Patrick’s Day storm is one of the most intense geomagnetic storm in this present solar cycle (SYM-H = -213nT). In this paper, we investigate the response of the African low latitude ionosphere to this storm event using the Total Electron Content (TEC) derived from four Global Positioning System (GPS) measurements in the region. The responses were also compared with that of 2013 (SYM-H = -132nT). The results obtained show that the deviation of TEC magnitude from quiet-time average behavior is generally is larger in 2015 than 2013. The effect is much larger during the recovery than the main phase for both storm events. In 2013, considerable TEC enhancement ( %ΔTEC > +25% for at least 3 consecutive hours) marks the minimum depression of SYM-H at Libreville and the prenoon periods of the first day of the recovery phase at MAL2 and ZAMB. Also, positive phases dominates at the equatorial stations while negative phases dominates at the low-latitude station during the 2013 storm recovery phase, suggesting the suppression of Equatorial Ionization Anomaly (EIA) by inhibiting prereversal enhancement vertical ion drift. In 2015, depletion marks the minimum downward excursion period while enhancement marks the prenoon. Further depletion marks the postnoon and postsunset periods of the first recovery day at the equatorial stations in 2015.For other recovery days, negative storm phases dominates low latitude (MBAR and MAL2), extending for about 36 hours, particularly around the midday, post-sunset and midnight. Comparison with other works shows distinct responses at different sectors.