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Abstract
The F2 region peak electron density (NmF2) morphology and the height of electron density (hmF2) response was investigated over Ilorin (lat. 8.31°N, long. 4.34°E, dip lat. 2.95o), a station along the equatorial anomaly trough, during Low Solar Activity (LSA). Diurnally, NmF2 and hmF2 are visibly more prominent during the daytime than the nighttime, having two characteristic peaks: pre-noon and post-noon peaks, except in hmF2 that has post-sunset peak during the nighttime. The NmF2 pre-noon peak with a magnitude range: (7.3–8.6) × 1011 /m-3 is observed around 0800–0900 LT, while hmF2 of magnitude range: (316–353) km is observed around 1000 LT. The NmF2 post-noon peak magnitude range: (6.7–11.7) × 1011 /m-3 is observed around 1500 and 1800 LT, while hmF2 post-sunset peak magnitude range: (310–392) km is observed around 1800 and 1900 LT during the entire season. In general, the pre-noon peak magnitude is less compared to the post-noon/post-sunset peak magnitude for all seasons. Seasonally, the NmF2 highest magnitudes were reached during the post-noon in the equinoctial months. The hmF2 highest magnitudes during post-sunset peak were observed in solstices, and also, annually, the post-noon/post-sunset peak is higher than the pre-noon peak for all the seasons. The rapid electron drift in hmF2 away from the equator is responsible for the sharp drop in NmF2 after sunset in all seasons. Seasonal peaks in general are suspected to be controlled by the enhanced E × B drifts and the atmospheric wind.
Keywords: NmF2; hmF2; Pre-noon peak; Post-noon peak; Post-sunset peak; Equator anomaly; Low Solar Activity,