Coherent nonlinear structures of drift wave turbulence modulated by zonal flows

Abstract

We investigate nonlinear stationary structures in a system of coupled equations describing drift wave turbulence and associated self-consistent zonal flows. The short-scale drift wave turbulence is described by a kinetic wave equation for the action density of drift waves, whereas the longer-scale zonal flows are described by a dynamic equation for the m = n = 0 (toroidally and poloidally symmetric) component of the potential. Nonlinear stationary structures in a moving frame can be obtained by retaining novel effects associated with 'trapped' and 'untrapped' drift wave trajectories. We show that drift wave turbulence can self-consistently sustain coherent, radially propagating modulation envelope structures such as solitons, shocks, nonlinear wave trains, etc.