Positioning of Ionospheric Irregularities and the Earth’s Surface Roughness Using an Over-the-Horizon HF Radar

We realize the possibilities for positioning of ionospheric irregularities and the Earth’s surface roughness with the chirp-signal ionosonde–radio direction finder used as an over-the-horizon HF radar of bistatic configuration on the Cyprus — Rostov-on-Don and Australia — Rostov-on-Don paths. It is established that the small-amplitude diffuse signals coming from azimuths of 310^°–50^° on the Cyprus — Rostov-on-Don path in the evening and at night at frequencies above the maximum observable frequency (MOF) of the forward signal are due to backscattering by small-scale irregularities of the mid-latitude ionospheric F Layer. It is shown that the backward obliquesounding signals recorded on the Cyprus — Rostov-on-Don path are caused by the sideband scattering of radio waves from the Caucasus mountain ranges, the Iranian highlands, and the Balkan mountains. It is found that the anomalous signals observed on the Alice Springs (Australia) — Rostov-on-Don path, which come from azimuths of 10^°–25^° with delays by 10–16 ms exceeding the delay of the forward signal are due to scattering of radio waves by the high-latitude ionospheric F-layer irregularities localized in the evening sector of the auroral oval at latitudes of 70^°–80^° N.