Morning overshoot of T_e enhanced by downward plasma drift in the equatorial topside ionosphere

The morning overshoot in electron temperature, T_e, which occurs in the sunlit atmosphere of low electron density during early morning hours, is a well known phenomenon. Studies of the phenomenon carried out using the Hinotori satellite observations reveal that the overshoot enhances in the topside equatorial F-region for a short period of time in the morning. The enhancement in the overshoot is found to depend on season and solar activity; it is strong during the northern summer months and grows with the increase in solar activity. Theoretical model calculations show that the enhancement in T_e is caused by a reduction in electron density in the topside ionosphere due to a downward drift of plasma.