Features of the effect of the Earth’s ionosphere on the field of an ordinary wave in the vicinity of the caustic

Abstract

The structure of the electromagnetic wave field in the vicinity of the caustic in the case of propagation in magnetically active ionospheric plasma near the surface of the earth is considered. A comparison of the uniform (caustic) approximation and the non-uniform (ray) one is performed. It is shown that the maximum value of the field amplitude in the vicinity of the caustic can be estimated from the geometrical-optical (ray) approximation. The calculations were performed both taking into account and without taking into account absorption, as well as taking into account the divergence of the radio signal in an anisotropic plasma for the model of night electron concentration and collision frequency of the high-latitude ionosphere. An estimate of the field on the caustic based on the ray approximation is proposed.