Effect of magnetic storms (substorms) on HF propagation: A review

The manifestations of the so-called main ionospheric effect during geomagnetic storms (substorms) in the character of decameter-wave propagation are analyzed. On HF radio paths, the main effect is observed as variations in the signal amplitude and the MOF-LOF working frequency band similarly to the critical frequency of the ionospheric F2 layer. Specifically, these parameters increase before the disturbance active phase, decrease during the active phase, and increase again after this phase. The propagation outside the great circle arc, the change in the propagation processes, and the HF radio noise behavior were also considered on these paths during storms (substorms). It is assumed that the storm (substorm) development onset can be predicted.