Interaction of Fully-Nonlinear Internal Solitary Waves with Cores

Under appropriate background conditions internal solitary waves may have surface or subsurface cores. Both types of waves have been observed in the ocean. Solutions of the Dubreil-Jacotin-Long equation predict cores with closed isopycnals and, in a reference frame moving with the wave, closed streamlines. In numerical simulations of a time-evolving field these cores are unsteady and leaky: fluid is continually being entrained into the core and leaking out of the rear of the core. In this talk I will present results of the interaction of two internal solitary waves, one with a core over-taking a smaller wave without a core. In general, during the interaction the large ISW decrease in amplitude while transferring energy to the smaller ISW. During this process the large ISW loses its core and the fluid inside the core is left behind. The smaller wave grows in amplitude and forms a new core. In many cases the final small ISW is considerably smaller than the initial small ISW while the larger ISW may be larger than the iniitial ISW. ISW energy is also transferred to small amplitude internal waves.