Abstract:
The present work investigates the seasonal dependence of the geomagnetic activity influences on the diurnal variability of the maximum electron concentration of the ionosphere over Bulgaria. Data from the ionosonde station Sofia for the period of 1995-2014 are used. The geomagnetic activity is described by the planetary Kp-index. The ionospheric response to the geomagnetic storms is studied by considering the relative deviation of the diurnal variability from its median course for the two ionospheric characteristics foF2 (critical frequency of the ionospheric F-region) and MUF3000 (maximum usable frequency for a distance of 3000 km). It is found that the ionospheric reaction in summer is stronger than that in winter and the time delay of the ionospheric response in winter is longer than that in summer.