Magnetic storm effects in H and D components of the geomagnetic field at low and middle latitudes

The paper describes the storm time (Dst) variations in horizontal (H) and eastward (Y) components of the geomagnetic field at stations along the Indo-Russian longitude sector. The location of stations extends from magnetic equator to polar latitudes but confined within narrow range of longitudes, thereby the results are not affected by any longitudinal inequalities. Both H and Y are shown to be significantly affected by magnetic storms. The storm time variation in H followed fairly well with the corresponding variation of Dst index, decreasing with increasing latitude, but the magnitude of ΔY increases with increasing latitude of the station. Further the Dst in Y was confined to period of the main phase when interplanetary magnetic field was southward. Thus, the recovery in Y is faster than that in H. Simultaneous changes of ΔY and ΔH follow the relation ΔY=ΔHsin(Ψ-D) where Ψ and D are the dipole and dip declinations at the station. The fluctuations in ΔY show better relationship with AE index than with Dst index. It is suggested that the ring current is energized occasionally by the injection of particles from even the sub-auroral latitudes along the earth's magnetic field lines.