Variations of nighttime enhancement in neutral and ion temperatures

Abstract:

The midnight temperature maximum (MTM) over equatorial region has been reported since 1970s, while the recently reported enhancement of the nighttime thermospheric and ion temperatures at middle and high latitudes is suggested extending from the equatorial region. Recently, we used both ground-based and satellite measurements to investigate the solar activity, seasonal and latitudinal dependences of the nighttime temperature variation at different latitudes. It was found that the postmidnight enhancement occurred in neutral and ion temperatures over middle and high latitudes with a seasonal dependence. Moreover, the CHAMP neutral density data were used to reveal the averaged patterns of the signature of the MTM, which shows the extension of the nighttime enhancement from the equatorial region to higher latitudes. In this presentation, we will also compare the observed data with the results from the coupled ionosphere and thermosphere model to explore the possible mechanisms responsible for the nighttime temperature enhancements at different latitudes.