Gaussian beam tracing for computing ocean acoustic fields

Abstract

The method of Gaussian beam tracing has recently received a great deal of attention in the seismological community. In comparison to standard ray tracing, the method has the advantage of being free of certain ray-tracing artifacts such as perfect shadows and infinitely high energy at caustics. It also obviates the need for eigenray computations. The technique is especially attractive for high-frequency, range-dependent problems where normal mode, FFP, or parabolic models are not practical alternatives. The Gaussian beam method associates with each ray a beam with a Gaussian intensity profile normal to the ray. The beamwidth and curvature are governed by an additional pair of differential equations, which are integrated along with the usual ray equations to compute the beam field in the vicinity of the central ray of the beam. We have adapted the beam-tracing method to the typical ocean acoustic problem of a point source in a cylindrically symmetric waveguide with depth-dependent sound speed. We present an overview of the method and a comparison of results obtained by conventional ray-tracing, beam-tracing, and full-wave theories. These results suggest that beam tracing is markedly superior to conventional ray tracing.