Spatial irregularity of the midlatitude ionosphere during strong geomagnetic storms

The spatiotemporal structure of the midlatitude ionosphere during strong geomagnetic storms (Dst < -300 nT) is studied by analyzing ionospheric characteristics and the total electron content. The study uses the data from three ionospheric stations (foF2m, h'F) and the results of total electron content measurements (N-t). The parameters foF2 and N-t, are found to vary synchronously during quiet periods and to show substantial quantitative differences during storms. An unusually strong increase in N-t(85%) compared to that in foF2(27%) was recorded during the peak of the geomagnetic disturbance and low solar activity. During a period of high solar activity, two-hour periods in the variations of foF2, a lowering of hmF2, and an increase in fmF2 were observed.