Response of the high latitude HF skywave channel to an isolated magnetic disturbance

Attention is focussed on the spread-F condition generated by a magnetic disturbance and the attendant consequences for the HF skywave channel. The results of an isolated magnetic perturbation of magnitude 200 γ(1 γ=10^-5 gauss) and of approximately one hour duration are described. The event was preceded by an extended period of magnetically quiet conditions. Experimental results showed that delay spreads are larger on the spread-F channel than on the quiet channel. The largest Doppler spreads are observed under spread-F conditions. Measured Doppler spreads vary, on average, by a factor of about 35 between quiet and very disturbed conditions