Angular characteristics of radio pulses reflected from the subpolar ionosphere

Abstract

This paper presents the results derived by measuring angular spectra of HF-radio pulses reflected from the subpolar ionospheric F2-region (62°N) using vertical-incidence soundings and a phase direction finder with Doppler filtering. The results correspond to three main types. One is the classical mirror reflection from the undisturbed ionospheric F2-region, typical of mid-latitudes (deviations from zenith do not exceed 3°; the angular spectrum width is less than 1°). The second type includes oblique diffuse reflections with a deviation from zenith of from 10 to 45°. The azimuth of arrival of these reflections is distributed in the range from 0 to 360°, the angular spectrum width is from 5 to 10°, and the range varies from 400 to 600 km. The third type includes anomalous mirror reflections with small deviations from zenith (not greater than 3°) but with substantially larger detection ranges (for example, 500km) as compared with the main reflections (250–300 km).