Dynamics of sunspot cycle ascending and descending phases asymmetry in equatorial ionospheric variability

Ionospheric variation from the climatological mean has been extensively studied due to its effect on ionospherichigh 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 daytimeand varies with season but with no consistent pattern. There is an earlier post-midnight peak variability in Junesolstice (around 0100LT) and occurred between 0400 and 0500LT in other seasons for all sunspot classificationsexcept solar maxima. In this study, we have paid attention to features in the ascending/decending phase of thesunspot cycle and we observed that nighttime ionospheric variability may not always decrease with increasingsunspot number, particularly in the ascending phase. The mechanisms for the difference between observations inthe ascending and descending phases could not be identified