Self-consistent turbulence in the two-dimensional nonlinear Schrödinger equation with a repulsive potential.
The dynamics of dark solitons (vortices) with the same topological charge (vorticity) in the two-dimensional nonlinear Schrödinger (NLS) equation in a defocusing medium is studied. The dynamics differ from those in incompressible media due to the possibility of energy and angular momentum radiation. The problem of the breakup of a multicharged dark soliton, which is a local decrease of the wave function intensity, into a number of chaotically moving vortices with single charge, is studied both analytically and numerically. After an initial period of intensive wave radiation, there emerges a nonuniform, steady turbulent self-organized motion of these vortices which is restricted in space by the size of the potential well of the initial multicharged dark soliton. Separate orbits of finite widths arise in this turbulent motion. That is, the statistical probability to observe a vortex in a given point has maxima near certain points (orbit positions). In spite of the fact that numerical calculations were performed in a finite region, the turbulent distributions of the vortices do not depend on the size of the container when its radius is larger than the size of the potential well of the primary multicharged dark soliton. The steady turbulent distribution of vortices on these orbits can be obtained as the extremal of the Lyapunov functional of the NLS equation, and obeys some simple rules. The first is the absence of Cherenkov resonance with linear (sound) waves. The second is the condition of a potential energy maximum in the region of vortex motion. These conditions give an approximately equidistant disposition of orbits of the same number of vortices on each orbit, which corresponds to a constant rotating velocity. The magnitude of this velocity is mainly determined by the sound velocity. An integral estimation of the self-consistent rotation of the vortex zone is given.
Ivonin
I A
IA
RRC Kurchatov Institute, 123182 Moscow, Russia.
Pavlenko
V P
VP
Persson
H
H