# Rays, modes, wavefield structure, and wavefield stability Academic Article

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### abstract

• Sound propagation is considered in range-independent environments and environments consisting of a range-independent background on which a weak range-dependent perturbation is superimposed. Recent work on propagation of both types of environment, involving both ray- and mode-based wavefield descriptions, have focused on the importance of $\alpha$, a ray-based stability parameter,'' and $\beta ,$ a mode-based waveguide invariant.'' It is shown that, when $\beta$ is evaluated using asymptotic mode theory, $% \beta =\alpha .$ Using both ray and mode concepts, known results relating to the manner by which $\alpha$ (or $\beta$) controls both the unperturbed wavefield structure and the stability of the perturbed wavefield are briefly reviewed.

• March 2005