Study of the evolution of Te and Ti at the low-latitude upper ionosphere using SROSS-C2 RPA observations

The SROSS-C2 satellite Retarding Potential Analyser measurements during 1995-2000 is used to make a direct comparison of electron and ion temperatures at the low-latitude upper ionosphere. The temperatures T-e and T-i exhibit prominent diurnal and solar cycle and weak seasonal variations. Both T-e and T-i exhibit similar diurnal features with morning and evening enhancements. Characteristics of these enhancements are found to evolve with season, altitude, latitude and solar activity. The daytime and nighttime mean values of electron and ion temperatures at the low-latitude ionosphere evolve differently and exhibit different long-term variations over minimum to maximum of a solar cycle. The nighttime mean values of T-e and T-i during 1995-2000 increase with solar activity indicated by the solar radio flux. Whereas the daytime mean values of T-e decrease with solar activity and the daytime mean value of T-i do not exhibit the solar cycle evolution. (C) 2004 Elsevier Ltd. All rights reserved.