Coupling of Acoustic Modes in the Ocean, A Comparison of Approximate Solutions
The representation of the acoustic field in a waveguide in terms of an infinite sum of normal modes is exact. However, when the properties of the waveguide are range-dependent, the modes (and their associated eigenvalues) can only be defined locally. The range variation of the amplitudes of the modes is a coupled set of ordinary second order differential equations. Under some conditions the coupling can be neglected and one obtains the adiabatic approximation to the solution1, 2. We have discussed elsewhere3, 4 the conditions of validity of the adiabatic solution by carrying out a formal asymptotic series solution. It was found that for typical mesoscale eddies in the ocean coupling could be significant. Further modelling presented here confirms those findings.
Unable to display preview. Download preview PDF.
- 3.Y. Desaubies, A uniformly valid solution for acoustic normal mode propagation in a range varying ocean. J. Acoust. Soc. Am., 76, 624–626.Google Scholar
- 4.Y. Desaubies, C.S. Chiu, J. Miller, Acoustic mode propagation through mesoscale eddies in the ocean. J. Acoust. Soc. Am., submitted (1985).Google Scholar
- 6.C.A. Boyles, Acoustic waveguides. John Wiley and sons, 321 pp. (1984).Google Scholar
- 7.F.W. Sluijter, Arbitrariness of dividing the total field in an opti cally inhomogeneous medium into direct and reversed waves. J. Opt. Soc. Am., 60, 8–10.Google Scholar