Detailed analysis of the behavior of the F2-layer critical frequency prior to geomagnetic storms

Abstract

A detailed analysis of the dependence of the number of events (critical frequency foF2 deviations on prestorm days from quiet conditions) and their intensity on the intensity of the coming magnetic storm and solar activity is performed. In order to separate the effects of the dependence on different parameters, the dependence on solar activity is considered for narrow intervals of Dst, (the measure of the storm intensity), whereas the dependence on the storm intensity is considered for narrow intervals of the F10.7 index characterizing solar activity. The conclusions on the decrease of the aforementioned numbers under an increase in the negative value of Dst (intensification of the storm) and F10.7 (solar activity increase) are confirmed. In is found that an increase in the event intensity is observed at intensification of the storm and that the intensity decreases at an increase in F10.7. The results of the analysis separately for each prestorm day shows that both the number of the events and their intensity are decreasing with remoting from the storm beginning (a transition from the zero days to other days).