On relation between characteristics of the subauroral ionosphere and plasma disturbances in the geostationary orbit: observatory Yakutsk (62.02° N, 129.72° Е), May-June 2003

Variations in the F2-layer critical frequency observed at the subauroral ionospheric station Yakutsk in May-June 2003 are considered. We mark out 12 days, during which the maximum diurnal variations in f 0F2 followed by its decrease, occurred earlier than on quiet days, and the minimum /0F2 was 0F2 occurred on the days when the magnetospheric convection field intensified, temperature of magnetospheric ions and electrons rose, and coefficients of their temperature anisotropy decreased to zero and negative values. The abrupt decrease in /0F2 coincided (within 30 minutes) with increase in the electron temperature in the geostationary orbit. In 2 cases, a significant early decrease in /0F2 was observed during the main phase and at the maximum of two moderate magnetic storms; it followed the weakening of the magnetospheric convection field and the decrease in temperature of magnetospheric electrons. The findings confirm the connection between the plasma sheet expansion in an earthward direction, the equatorward shift of the main ionospheric trough and the abrupt decrease in the subauroral F2-layer critical frequency that has been revealed earlier using data from ground-based stations and low-orbit satellites.