A spectral-domain method for multiple scattering in continuous randomly irregular media

A spectral-domain method for computing the first and second-order moments of a scalar wavefield propagating in a continuous randomly irregular medium is described. The scattering is characterized by the moments of incremental forward and backward scattering functions. Approximate forms for these moments are given in terms of the spectral density function of the relative permittivity fluctuations. Solutions are developed for incident plane and spherical waves. Well-known results that are usually derived from the parabolic wave equation using the Markov approximation are easily recovered from the general solutions. The results show that backscatter enhancements depend on the correlation between the forward and backward scattered waves. Computations are performed to illustrate the effects of backscatter on VHF transionospheric radiowaves