LAUSR

Abstract Ionospheric variation from the climatological mean has been extensively studied due to its effect on ionospheric high frequency radio propagation. This work reports foF2 variation at Ouagadougou (geogr. 12oN, 1.8oW, dip ∼3°), complementing works that have been done at this station. Nighttime variability is higher than daytime and varies with season but with no consistent pattern. There is an earlier post-midnight peak variability in June solstice (around 0100LT) and occurred between 0400 and 0500LT in other seasons for all sunspot classifications except solar maxima. In this study, we have paid attention to features in the ascending/decending phase of the sunspot cycle and we observed that nighttime ionospheric variability may not always decrease with increasing sunspot number, particularly in the ascending phase. The mechanisms for the difference between observations in the ascending and descending phases could not be identified.