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 during geomagnetically disturbed periods are known to exhibit significant deviations from atmospheric model predictions. Also, the oscillatory features seen in the observations are not accounted for by the models. A simple relation has been established between the difference in the observed 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 temperatures spectroscopically determined from Mt. Abu, a low-latitude station in India, are successfully reproduced for two moderate geomagnetic storms.