Magnetic storm effects on the variation of TEC over Ilorin an equatorial station

Abstract

We have used total electron content (TEC) derived from dual-frequency GPS receivers to study magnetically quiet and storm time variations of the ionosphere at Ilorin(8.47°N, 4.68°E), an equatorial station in the African sector. Four years (2009-2012) data were used for the study. The result on the quiet time variation of the ionosphere showed that the diurnal variation of TEC is not symmetrical about noon. This is a departure from a typical Chapman variation. Daytime maximum occurred after local noon (13-16 LT) for all the seasons and at all solar activity levels considered. A significant effect of solar activity variation was observed on the seasonal trend in 2011. The tendency for magnetic storms to cause increases in TEC is much greater than those of decreases. Daytime maximum TEC usually occurred closer to the noon time during storm periods when compared to those of quiet periods. Maximum percent change in TEC on storm days varied from about 25 to 131%.