A HYBRID SPLIT-STEP FINITE-DIFFERENCE PE ALGORITHM FOR VARIABLE-DENSITY MEDIA/

Although variations in the density, rho, are naturally incorporated in to finite-difference parabolic equation (PE) solvers, split-step PE al gorithms traditionally account for density changes by adding to the re fractive index terms containing derivatives of rho. As a consequence, geoacoustic density profiles that contain step discontinuities at laye r interfaces must be smoothed appropriately before these extra terms c an be evaluated. In this paper, a new hybrid method is proposed for tr eating density inhomogeneities in the split-step PE. This approach inv olves splitting the differential operator into density-independent and density-dependent components. While the former terms may be evaluated with the split-step Fourier technique, the influence of density chang es is handled through a finite-difference procedure. Such an algorithm can be easily implemented in recently proposed hybrid split-step/fini te-difference and split-step/Lanczos PE solvers. [J. Acoust. Sec. Am. 96, 396-405 (1994)].