Season, local time, and longitude variations of electron temperature at the height of ∼600 km in the low latitude region

Abstract

Electron temperature observed at the height of ∼600 km by the low inclination satellite Hinotori was studied in terms of local time, season, latitude, magnetic declination and solar flux intensity. The electron temperature shows a steep rise in the early morning (well known as “morning overshoot”), a decrease after that and again an increase at ∼18 hours (hereafter named “evening overshoot”). Generally the morning overshoot becomes more enhanced in the winter hemisphere and during higher solar flux. The evening overshoot becomes more pronounced in the higher latitudes in all seasons and more enhanced in the winter hemisphere as similar to the morning overshoot. These two overshoots show a slight difference in the 210° – 285° and 285° – 360° longitude sectors. This is most likely due to the difference in magnetic declination of these two zones and the resulting difference in the effect of the zonal neutral wind on the thermal structure in the low latitude ionosphere. Significant difference exists between IRI and the observation during daytime.