Seasonal and solar activity changes of electron temperature in the F-region and topside ionosphere Original Research Article

Incoherent scatter radar data from Arecibo, for high solar activity (HSA) (1989–1990) as well as for low solar activity (LSA) (1974–1977) periods, are used to study the seasonal and solar activity variations in electron temperature (Te) for noontime conditions. Inspite of large day-to-day variations, clear seasonal variations in average Te can be identified for both solar activity periods, with winter temperatures significantly higher in the topside (400–700 km) ionosphere. Further, comparison of average Te profiles for each season reveals distinct solar activity variations – a large increase in the F-region (200–350 km) Te, during summer and equinox as compared to winter, occurs as one moves from low to HSA. In the topside, however, electron temperature changes little with solar activity. Comparisons with IRI-95 and models show a reasonable agreement within one standard deviation of the measured values.