The caustic and ray structures of reflected waves in a linear plasma layer

Abstract

The caustic and ray structures formed during propagation of electromagnetic waves in a plasma layer are studied in the case when the effective permittivity of the propagation medium linearly decreases as the altitude grows. The main attention is focused on the caustic structure of reflected rays that have various orders and are observed during multihop propagation and tilt-sounding ionograms. It is shown that the caustic structure of a reflected wave corresponds to a hyperbolic umbilic (a D ⁺₄ catastrophe) and that taking into account reflection results in ionogram spreading.