Features of the Diurnal Variation of Electron and Ion Temperatures in the Low Latitude Upper Ionosphere
Lalitha T. Alexander

Abstract
The electron temperature Te and the ion temperature Ti was found to exhibit a sharp morning enhancement, a day time trough, evening enhancement and stable night-time value. At sunrise the photoelectron production begins in the ionosphere through the ionization of the neutral particles .As the photoelectrons share their high energy with the ambient electrons, the electron temperature (Te) increases. This increase is rapidly in the early morning hours due to the low electron density. As more and more electrons are produced the sharing of energy for each electron decreases. After reaching a maximum decrease and attains a steady state as the day progress. The SROSS C2 satellite has provided some valuable data on the thermal structure of the topside ionosphere over the Indian region. The Japanese Hinotori satellite, which had a near circular orbit at 600 km, provides an ideal database for studies of temporal and spatial variations of electron temperature in the topside ionosphere. The temperatures Te and Ti are found to have similar diurnal variations. The morning and evening peaks arise basically from the photoelectron heating of the morning and evening electron gas. The diurnal pattern of Te and Ti clearly shows the morning overshoot, evening enhancement, daytime valley and night-time stability.

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