Effects of neutral wind on the electron temperature at a height of 600 km in the low latitude region

Abstract. Electron temperature observed by the Hinotori satellite with the low inclination at the height of ~600 km was studied in terms of local time, season, latitude, magnetic declination and solar flux intensity during a 16-month period from 1981 to 1982. The electron temperatures show steep rise in the early morning (well known as morning overshoot), decrease after that and again increase at ~18 hours (hereafter named as evening overshoot). Generally the morning overshoot becomes more enhanced in the winter hemisphere and for higher solar fluxes. The evening overshoot becomes more pronounced in the mid-latitude in all seasons and more enhanced in the winter hemisphere in the same way as the morning overshoot. A difference is seen between 210°–285° and 285°–360° longitudes where magnetic declination is different. The longitudinal dependence of electron temperature indicates that the neutral wind also contributes to the thermal structure in the low latitude ionosphere.