FORWARD PROPAGATION IN A HALF-SPACE WITH AN IRREGULAR BOUNDARY

The parabolic wave equation (PWE) has been used extensively for modeli ng the propagation of narrow beams in weakly inhomogeneous random medi a. Corrections have been developed to accommodate wider scattering ang les and boundaries have been introduced. Nonetheless, the formalism re mains approximate and irregular surfaces with general boundary conditi ons present difficulties that have yet to be overcome. This paper pres ents an alternative approach to the entire class of propagation proble ms that strictly involve forward propagation, Forward-backward iterati on has recently been shown to be a powerful procedure for computing th e source functions that support propagation over irregular boundaries at low grazing angles, In this paper, we show that the source function s for any unidirectional sweep can be computed by using a marching sol ution. This is not only more efficient than the single-sweep computati on, but it facilitates accommodation of inhomogeneities in the propaga tion media, An exact equation for forward propagation in unbounded inh omogeneous media is used to derive a correction term that is applied a t each forward-marching step. Results that combine ducting atmospheres and rough-surface scattering effects are presented for both the Diric hlet and Neumann boundary conditions.