Seasonal dependence of the response of the low latitude thermosphere for external forcings

Using the in situ measured neutral temperatures: by the DE-2 satellite. the D-st geomagnetic index which is a measure of the intensity of earth's ring current along with the MSIS model predictions, the low latitude thermosphe re has: been shown to have a delayed response to any energy input over pola r regions with the time delay revealing a seasonal dependence. The response time has been observed to vary between 8 and 20 h from summer to winter. I nterestingly, the response sensitivity of the thermosphere for any change i n D-st index remained nearly the same throughout the year implying other fo rcings to he responsible for the observed seasonal dependence. These aspect s are presented and discussed. (C) 2001 Elsevier Science Ltd. All rights re served.