An empirical model of electron temperature in the Indian topside ionosphere for solar minimum based on SROSS C2 RPA data

Abstract

An empirical model of electron temperature ( T e) for Indian equatorial and low latitudes at the altitude of 500 km is presented. The model, applicable for low solar activity, is based on the observation that electron temperature and electron density ( N e) in the F region of the Indian equatorial and low latitude ionosphere are inversely correlated during the daylight hours (0600–1800 LT) at all latitudes and in all seasons. Nighttime (1900–0500 LT) T e was found to be independent of N e. Electron temperature and electron density measured by the Retarding Potential Analyzer (RPA) instrument on board the Indian SROSS C2 satellite during the solar minimum period January 1995 to December 1996 have been used to derive the relationship between T e and N e. The satellite observations correspond to an average altitude of 500 km. Regression coefficients were obtained from least square fits for all data during daylight hours from 10°S to 15°N magnetic latitudes at 5° intervals. Using the coefficients and corresponding N e data for summer, winter and equinox, T e was calculated for the daylight hours. Average nighttime T e was taken as the model value for these hours. Latitudinal profiles were obtained employing a system of associated Legendre polynomials. The modelled and observed electron temperature was compared and found to be in good agreement. The model is limited to fixed altitude and low solar activity conditions.