Jovian acoustic tomography

Abstract

Recent work in ocean acoustic tomography indicates that acoustic waves propagating global distances contain planetary-scale information [A. B. Baggeroer and W. Munk, Phys. Today 45(9), 22–30 (1992)]. The expected collision of the fragments of comet Shoemaker–Levy 9 with Jupiter in July [J. K. Beatty and D. H. Levy, Sky & Telescope 87(1), 40–44 (1994)] provides an opportunity to explore the use of techniques developed in ocean acoustics on a different planet. The nonlinear progressive wave equation [B. E. McDonald and W. A. Kuperman, J. Acoust. Soc. Am. 81, 1406–1417 (1987)] can be used to model the propagation of shock waves near the impact sites. Adiabatic modes can be used to determine horizontally refracted propagation paths on an oblate spheroid [Heaney etal., J. Acoust. Soc. Am. 90, 2586–2494 (1991)]. Normal-mode and parabolic equation (PE) models can be used to obtain two-dimensional (range and depth) solutions, which illustrate geometric dispersion and cycle distances. The adiabatic mode PE [M. D. Collins, J. Acoust. Soc. Am. 94, 2269–2278 (1993)], generalized to include horizontal wind fields, can be used to determine the horizontal distribution of energy and the locations of caustics. Available input data (from the Voyager missions and other sources) for making pre-impact predictions include wind velocity as a function of latitude, the locations of the impacts, and information for estimating sound speed as a function of depth.