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

Abstract

The diurnal, seasonal and latitudinal variations of electron temperature Te, 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 ~500 km and it covered the latitude belt of -31° to 34° and the longitude range of 40°-100°. Te varies between 700-800 K during nighttime (20:00-04:00 LT), rises sharply during sunrise (04:00-06:00 LT) to reach a level of ~3500 K within a couple of hours and then falls between 07:00-10:00 LT to a daytime average value of ~1600 K. A secondary maximum is observed around 16:00-18:00 LT in summer. Latitudinal gradients in Te 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 Te well within ~ 100 K of observation, but at other local times, the predicted Te is less than that measured in all seasons.