Variation of Vertical Total Electron Content (TEC) Over West Africa during Geomagnetic Storms

Changes in vertical total electron content (VTEC) over West Africa which were associated with four geomagnetic storms in 2015 have been studied. The spatial evolution of the quiet time TEC over West Africa for four months (vis; March, June, October and December) which may give rise to unique features of the storm TEC were also evaluated. Quiet-time VTEC (i.e Sq VTEC) was obtained using the hourly means of the international quietest days for each month when a storm of interest occurred. The change in TEC ( ) was obtained after removing the quiet time VTEC from the storm day VTEC. A significant latitudinal variation in VTEC was observed at 22:00LT over West Africa and this was accompanied by the usual broad peak at about 14-17UT. The latitudinal disparity observed in the Sq at 22.00LT was likely driven by the intesification of the fountain effect. The maximum observed during the storms in 2015 were of the other of 16 TECU. These results have important implications for our present understanding of TEC evolution during a geomagnetic and its direct effect on the technologies that depend on it.