Morphology of Ionospheric foF2 And NmF2 over Ilorin during Low Solar Epochs

The F2 region critical frequency (f_oF2) and peak electron density (N_mF2) morphology was investigated over Ilorin (latitude 8.31°N, longitude 4.34°E) during a Low Solar Epochs (LSE), a station along the equator anomaly trough. Diurnally, f_oF2 and N_mF2 are visibly more prominent during the day than at night with two characteristic peaks: pre-noon and post-noon peaks. The f_oF2 and N_mF2 pre-noon peak magnitude range: (7.7–8.3 MHz) and (7.3–8.6) × 10¹¹ /m^-3respectively is less compared to the f_oF2 and N_mF2 post-noon peak magnitude range: (7.3–9.7 MHz) and (6.7–11.7) ×10¹¹ /m^-3 respectively. Seasonally, the highest values were attained during the post-noon peak in the equinoctial months compared to the solstices months, and also, annually, the post-noon peak is higher than the pre-noon peak. The rapid electron drift away from the equator is responsible for the sharp drop in f_oF2 and N_mF2 after sunset in all seasons. Seasonal peaks in f_oF2 and N_mF2 are suspected to be controlled by the enhanced E × B drifts and the onset and turn-off of solar ionization, which is consistent with some earlier results obtained at some stations in the African region during low solar epoch periods.