Space-time sound fluctuations due to internal solitons in shallow water

In this paper results of numerical modeling of sound propagation in shallow-water waveguide with internal waves are presented on the basis of experimental data about internal solitons (IS) registered in the Japan sea [A. N. Serebryany, Sov. Phys. Oceanol. 27, 225–226 (1987)]. These IS constitute some sequences of oscillations with amplitude up to 10 m moving toward coastal line with the velocity about 0.25 m/s. The wavelength of separate oscillations in this group is about 325 m; total length of the packet is about 4 km. Three-dimensional sound-speed distribution is constructed using the mentioned data. On the basis of this model, space-time fluctuations of intensity of the sound propagating in such medium are calculated. The modeling is carried out within the framework of the parabolic equation method in the horizontal plane and the modal approach in the vertical one. These fluctuations can be interpreted as the forming of a sound waveguide in the horizontal plane; space-time scales of fluctuations correlate with space-time scales of IS. Different numerical examples are presented; possible experimental setup is discussed. [Work supported by RFBR, Grant 00-05-64752.]