Application of ionospheric predictions to HF propagation in three dimensions

Abstract

The application of ionospheric predictions is extended to three‐dimensional HF propagation by using a simplified ray‐tracing technique involving an ionospheric model consisting of an equivalent spherical reflection surface eccentric with the earth. Predicted ray‐path deviations from the great‐circle plane and other propagation characteristics are investigated for a medium range midlatitude path by using the NOAA prediction coefficients. The predicted monthly mean diurnal behavior of the azimuthal angle of arrival of the HF signal is compared with experimental data. It is found that the observed occurrence of wave‐interference effects is strongly correlated with the predicted occurrence of multiple mode propagation and that the trend of the diurnal variation of the predicted azimuthal angle of arrival for the dominant mode is consistent with the average diurnal trend of the experimental observations.