HF radio propagation at high latitudes under quiet and disturbed geomagnetic conditions

High-frequency (HF) radio communications at high latitudes are greatly affected by geomagnetic and ionospheric conditions, and both civilian and military users need reliable forecasts of the propagation environment. In previous years, a network of channel sounders known as DAMSON (Doppler and Multipath Sounding Network) has been operated in Scandinavia (including Svalbard) on a nearly continuous basis. We have analysed DAMSON measurements of multipath spread, Doppler shift and spread, and signal-to-noise ratio on four HF paths under both quiet and disturbed geomagnetic conditions. Correlations have been made with data from a magnetometer network in the same geographic region. Long signal delays (several ms) are regularly observed during midday at frequencies well above the predicted MUF and could possibly be caused by ground scatter. Large Doppler spreads (tens of Hz) are observed during disturbed conditions (substorms), when the ionospheric reflection point is located within the auroral oval.