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

Abstract

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 (T_e) for noontime conditions. Inspite of large day-to-day variations, clear seasonal variations in average T_e can be identified for both solar activity periods, with winter temperatures significantly higher in the topside (400-700 km) ionosphere. Further, comparison of average T_e profiles for each season reveals distinct solar activity variations - a large increase in the F-region (200-350 km) T_e, 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 Truhlik et al. (2000) models show a reasonable agreement within one standard deviation of the measured values.