Effects of solar and geomagnetic activity in long-term variations in the ionospheric parameters of the auroral zone in 1963-1986

A stable linear relation between foF2 and W with a correlation coefficient of 0.68-0.96 has been revealed as a result of a joint analysis of the foF2 critical frequencies and the virtual minimal heights (h'F) obtained from the data of vertical sounding (VS) of the ionosphere at Dixon Island auroral station, Wolf numbers (W), and PC geomagnetic index from 1963 to 1986. A significant linear relation exists between foF2 and the PC index with a correlation coefficient of r = 0.18-0.67. The correlation between the PC index and W is low in winter and autumn and is r = 0.50 and 0.74 at a significance level of ss = 0.96-0.99 in spring and summer. When the correlation between PC and foF2 is analyzed, it is necessary to consider the effect of solar activity (SA) on both parameters. The multiple correlation coefficients between these parameters have been calculated with regard to the effect of W. They were R = 0.75-0.98; however, the standardized regression coefficients beta (W) and beta (PC) indicated that W and PC considerably and insignificantly affect multiple correlation with foF2, respectively, and this effect depends on the season and time of day. It has been detected that the cyclic variations in foF2 and h'F are asymmetric. The amplitudes of these parameters in cycle 20 are smaller than in cycle 21.