A correlation study between time-weighted magnetic indices and the high latitude ionosphere

Time weighted accumulations of the ap, AE and PC magnetic indices have been here analysed together with the hourly values of the critical frequency of the F2 ionospheric layer, foF2, coming from several ionospheric stations located in the European longitudinal sector at geographic latitudes ranged between 60°N and 68°N. The preliminary results obtained for different seasons and for different solar activity conditions indicate that the response time of the high latitude ionosphere to the magnetic activity is of the order of about 15 and/or 20 hours depending on the magnetic index considered.