Diurnal, seasonal and latitudinal variations of electron temperature measured by the SROSS C2 satellite at 500 km altitude and comparison with the IRI

The diurnal, seasonal and latitudinal variations of electron temperature T-e, measured by the SROSS C2 satellite at equatorial and the low-latitudes during the low solar activity period of 1995-1997 are investigated. The average height of the satellite was similar to500km and it covered the latitude belt of -31degrees to 34degrees and the longitude range of 40degrees-100degrees. T-e varies between 700-800K during night-time (20:00-04:00LT), rises sharply during sunrise (04:0006:00LT) to reach a level of similar to3500K within a couple of hours and then falls between 07:00-10:00LT to a daytime average value of similar to1600K. A secondary maximum is observed around 16:00-18:00 LT in summer. Latitudinal gradients in T-e have been observed during the morning enhancement and daytime hours. Comparison of measured and International Reference Ionosphere (IRI) predicted electron temperature reveals that the IRI predicts nighttime T-e well within similar to100K of observation, but at other local times, the predicted T-e is less than that measured in all seasons.