Ionospheric foF2 variability at equatorial and low latitudes during high, moderate and low solar activity

Abstract

This paper presents diurnal, seasonal and solar activity effects on the variability of ionospheric foF2 in the equatorial and low latitude regions. Three ionosonde stations, viz. Huancayo (12.0°S, 75.3°W, dip 1.8°N), Ouagadougou (12.4°N, 1.5°W, dip 2.8°N) and Vanimo (2.7°S, 141.3°E, dip 22.5°S) were considered for the investigation. Generally, the diurnal analysis revealed that the critical frequency of the F2 layer (foF2) is more susceptible to variability during the nighttime than the daytime, with two characteristic peaks, pre-sunset peak (12–50%) and post-midnight peak (22–70%). Seasonally, the June Solstice maximum was observed at Vanimo, while the peaks for other seasons were observed at Huancayo with the overall non-typical pattern of seasonal characterization for foF2 variability. At all stations, foF2 variability was noticed to be highest for the low solar activity year. Overall, equatorial foF2 variability increases with decreasing solar activity.