Chaos and Wavefront Reversal for Long-Range Sound Propagation

Long-range sound propagation in the deep ocean is considered. Attention is concentrated on the procedure of acoustic wavefield refocusing by means of the wavefront reversal. Temporal variations of oceanic medium in course of propagation from the probe source to the acoustic mirror and back violate the reciprocity principle and thereby lower efficiency of refocusing. It is shown that ray chaos caused by scattering on internal waves enhances sensitivity of the reversed wavefield to medium variations. An underwater sound channel crossing several synoptic eddies is considered as an example. It is shown that refocusing becomes almost impossible if distance between the probe source and the acoustic mirror exceeds 350 km. Nonetheless, one observes an anomalous zone of enhanced refocusing at distance of 300 km from the acoustic mirror.