Plasma drift observations associated with intense magnetic storms by the IPEI on board ROCSAT-1

We use the plasma drift observations from the Ionospheric Plasma and Electrodynamics Instrument (IPEI) on board the ROCSAT-1 satellite to study the midlatitude and low-latitude ionospheric response to intense magnetic storms during the period between year 2000 and 2003. The observations show that the perturbed vertical/meridional drifts result from the prompt direct penetration and/or disturbance dynamo electric fields can be simultaneously seen at different latitudes. The results also show that the temporal evolution of the perturbed zonal drifts is strongly correlated with that of the Dst index and clearly appears only in the nighttime, which is in excellent agreement with the model prediction from the National Center for Atmospheric Research Thermosphère Ionosphere Electrodynamics General Circulation Model (NCAR/TIEGCM). The model results indicate that during the intense magnetic storm time the meridional electric fields resulting from the disturbance dynamo can reach a value of about 5.6 mV/m in the nighttime; the maximum zonal electric fields are about 2 mV/m at around 0500 LT. This result indicates the nighttime zonal plasma drifts are controlled by the disturbance dynamo mechanism. In addition, one of the cases shows the appearance of long-lasting perturbation electric fields with time duration of about 7 h. The interesting point for this case is that it appears only in the nighttime and almost disappears in the daytime.