The dynamics and composition of the neutral thermosphere controlled by the difference sources of energy, some fundamental properties of the Geo-magnetic storms and their effects on the F-region ionization are discussed in this paper. The ionospheric electric fields and currents during both SC and GC types of geomagnetic storms and their importance are also presented in this paper. In the present study the scintillation data obtained from FLEETSAT radio beacon signal at 250.649MHz at near equatorial station, Anantapur (14.7° N, 77.7° E, and Dip 15.4 ° N) India, during some specific storm periods of varying strengths have been examined in association with the occurrence of maximum negative excursion of equatorial DST. The DST index, which is a measure of the ring current at low latitudes, has been used as a measure of the magnetic activity. The occurrence of maximum negative excursions in DST during the local pre-midnight and post-midnight hours is also presented in this paper.