Ray Tracing in the lonosphere

The problems of tracing rays in the ionosphere for radio propagation, primarily for high frequencies (3 to 30 MHz) and above, are discussed. The limitations on “classical” geometrical optics are described, and their applications to ionospheric problems are indicated. Some “simplified” processes of ray tracing, which apply well at the earth's surface, but not in the ionosphere itself, are first presented. Next, ray‐tracing methods which apply in an isotropic ionosphere, when the effects of the earth's magnetic field is negligible, are discussed. The results are then extended to more general cases of an isotropic medium, and, finally, to an anisotropic medium (such as the ionosphere in the presence of the earth's magnetic field). Certain special problems which must be considered in ray‐tracing studies are described next; and, finally, a few of the important areas for the application of ray tracing are noted.