Variation of the Critical Frequency of the Ionospheric F2 Layer during Moderate Geomagnetic Conditions: A Study Using Data from the Ouagadougou Ionosonde Station Across Solar Cycles 21 and 22

Abstract

This study investigates the variations in the critical frequency of the F2 layer (foF2) at the Ouagadougou ionosonde station during moderate geomagnetic activities, focusing on corotating and magnetic cloud events across the minimum and maximum phases of solar cycles 21 and 22. The analysis reveals significant perturbations in the diurnal profiles of foF2 during magnetic cloud activity at the solar minimum phase, compared to profiles observed during magnetically quiet activity. These perturbations indicate a disturbance of electrodynamic processes, including ionospheric currents and upward drifts. Conversely, corotating activity exhibits negligible impact on foF2 profiles at solar minimum phase. At solar maximum phase, the diurnal profiles observed during moderate geomagnetic activities are identical to those observed during very quiet days. Notably, ∆foF2 values during moderate activities are generally below 20% during the day but show short-lived positive storms (>20%) at night, especially near sunrise. These findings enhance our understanding of equatorial ionospheric dynamics and the influence of geomagnetic activity, contributing to improved space weather predictions and ionospheric modeling.