Dynamics of coherent structures and turbulence of plasma drift waves

A simple model based on the Hasegawa-Mima equation is used to study dipole vortex interactions and turbulence of electrostatic drift waves in a plasma. It is shown that if nonlinear effects are important during vortex collisions, dipoles are broken into monopoles. Nonadiabatic effects also affect dipole behavior, which can be destroyed by the instability of emitted waves (dipole vortex radiation). Simulations of turbulence in both decaying and driven cases show the appearance of long-lived monopole structures. These coherent structures contribute to stop the cascade of energy to large scales, and then to reach a self-organized stationary state. Some numerical evidence is done that Hasegawa-Mima turbulence has a long-time behavior that is much richer than the thermodynamic equilibrium state observed in two-dimensional hydrodynamics. In driven turbulence, an important departure from Gaussian statistics of vorticity fluctuations is found, giving some indication of intermittency. Using various analyzing techniques, in particular the proper orthogonal decomposition, we show that the turbulence can be characterized by a field of coherent structures, which dominates the dynamics of the system, and random waves interacting weakly with the coherent structures. (c) 1995 The American Physical Society © 1995 The American Physical Society.Fil:Verga, A. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina