Radio propagation in non-uniform media

It has been established that, in naturally occurring ice, exotic propagation modes exist for radio signals. An interesting consequence of this is that it seems possible for signals to propagate to the receiver from an area which lies in the expected shadow zone. We present a ray tracing script based on Fermat's principle that has been developed with the aim to model and understand these propagation modes. The results of this script have been found in agreement with an earlier prediction that over-densities are able to guide the ray paths. In addition to the in-ice problem of propagation modes we use this approach to evaluate approximations made in air-shower radio emission simulations and verify if the approximations break down for certain geometries.