Rays, modes, wavefield structure and wavefield stability
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
α
, a ray-based ``stability parameter,'' and
β,
a mode-based ``waveguide invariant.'' It is shown that, when
β
is evaluated using asymptotic mode theory,
β=α.
Using both ray and mode concepts, known results relating to the manner by which
α
(or
β
) controls both the unperturbed wavefield structure and the stability of the perturbed wavefield are briefly reviewed.