Comparative study of equatorial and high-latitude over-the-horizon radar parameters using ray-tracing simulations

Abstract

Certain parameters of over-the-horizon radars (OTHRs) need regular adjustment to keep constant illumination of a target due to ionospheric variability. Feasible values of these parameters for an OTHR operation, namely, the ranges of operating frequencies and elevation angles can be assessed using ray-tracing simulations, together with the reflection height in the ionosphere and absorption along the path. In this letter, a comparative study of these parameters is presented considering an equatorial and a high-latitude OTHR location using a 3-D ray-tracing code interfacing IRI-2016, IGRF, and absorption models. These geographic latitudinal regions present markedly different F2 region seasonal variation, E region ionization sources, and magnetic field conditions. Only the ionization characteristics have noticeable effects in our analysis. The main differences are observed in the lowest usable frequency during nighttime and in the seasonal variability of the maximum usable frequency due to E and F2 layers differences at the corresponding locations. Absorption is quite similar in both low- and high-latitude locations