Geomagnetic storm effects at low latitudes

The geomagnetic horizontal (H) field from the chain of nine observatories i n India are used to study the storm-lime and disturbance daily variations. The peak decrease in storm-time variation in H showed significant enhanceme nts at the equatorial electrojet stations over and above the normally expec ted decrease due to the ring current effects corrected for geomagnetic lati tudes. The disturbance daily variation of H at equatorial stations showed a large decrease around midday hours over and above the usual dawn-maximum a nd dusk-minimum seen at any mid-latitude stations around the world. These s low and persistent additional decreases of H of disturbance daily variation at equatorial latitudes could be the effect of a westward electric field d ue to the Disturbance Ionospheric dynamo coupled with abnormally large elec trical conductivities in the E region over the equator.