Effect of a cylindrically-symmetric ionospheric disturbance on ELF Propagation in the earth-ionosphere waveguide

A nuclear explosion in the earth's ionosphere produces a depression in the ionosphere that is approximately cylindrically symmetric. In this paper, a method is developed for calculating the change in amplitude and phase at a receiver of an ELF (extremely low frequency) radio wave in the presence of such a localized, cylindrically-symmetric disturbance. Numerical results are obtained for the particular configuration where the center of the disturbance is directly above the transmitter-receiver path. The attenuation from one edge of the disturbance to the opposite edge is found to be only about half of that calculated by the two-dimensional WKB approximation usually employed in such problems.