A CASE-STUDY OF THE LOW-LATITUDE THERMOSPHERE DURING GEOMAGNETIC STORMS AND ITS NEW REPRESENTATION BY IMPROVED MSIS MODEL

The thermospheric temperatures from low and equatorial latitudes durin g geomagnetically disturbed periods are known to exhibit significant d eviations from atmospheric model predictions. Also, the oscillatory fe atures seen in the observations are not accounted for by the models. A simple relation has been established between the difference in the ob served and model-predicted temperatures and the rate of change of Dst, the magnetic index representing the ring current variabilities. Using this relation, a correction term has been added to the latest MSIS-90 model algorithm and almost all the observed variations in neutral tem peratures spectroscopically determined from Mt.Abu, a low-latitude sta tion in India, are successfully reproduced for two moderate geomagneti c storms.