Relationships between magnetospheric and ionospheric disturbances in the auroral and subauroral zones

A joint analysis of variations in the ionospheric parameters at three vertical-incidence stations (Heiss Island, Dixon Island, and Sodankyla) and the solar wind plasma characteristics (i.e., the PC magnetic index characterizing the IMF geoeffective part) indicated that the PC index can be used as a predictor in order to diagnose the electron density level in the polar ionosphere. An increase in the PC level corresponds to positive and negative gradients in variations in the F region's critical frequencies. As PC becomes larger than 1.5, the electron density increases at night in winter and, on the contrary, decreases during the day in summer and during daylight hours in winter. A delay in the ionospheric F region's response to PC variations depends on the station latitude: this delay is no more than 1 and 2 h at the Heiss Island and Dixon Island stations and can be more than 6 h in summer and 0-1 h in winter at Sodankyla. An increase in the PC amplitude as a rule corresponds to an anomalous increase in foEs relative to the median values at these stations with a delay of 1 h.