Theory and applications of ray chaos to underwater acoustics - art. no. 036221

Chaotic ray dynamics in deep sea propagation models is considered using the approaches developed in the theory of dynamical chaos. It has been demonst rated that the mechanism of emergence of ray chaos due to overlapping of no nlinear ray-medium resonances should play an important role in long range s ound propagation. Analytical estimations, supported by numerical simulation s, show that for realistic values of spatial periods and sound speed fluctu ation amplitudes associated with internal-wave-induced perturbations, the r esonance overlapping causes stochastic instability of ray paths. The influe nce of the form of the smooth unperturbed sound speed profile on ray sensit ivity to the perturbation is studied. Stability analysis has been conducted by constructing the Poincare maps and examining depth differences of ray t rajectories with close take-off angles. The properties of ray travel times, including fractal properties of the time front fine structures, under cond ition of ray chaos have been investigated. It has been shown that the coexi stence of chaotic and regular rays, typical for dynamical chaos, leads to t he appearance of gaps in ray travel time distributions, which are absent in unperturbed waveguides. This phenomenon has a prototype in theory of dynam ical chaos called the stochastic particle acceleration. It has been shown t hat mesoscale inhomogeneities with greater spatial scales than that of inte rnal waves, create irregular local waveguide channels in the vicinity of th e axis (i.e., sound speed minimum) of the unperturbed waveguide. Near-axial rays propagating at small grazing angles, "jump" irregularly between these microchannels. This mechanism determines chaotic behavior of the near-axia l rays.