Multiscale interaction of a tearing mode with drift wave turbulence: A minimal self-consistent model

Abstract

A minimal self-consistent model of the multiscale interaction of a tearing mode with drift wave turbulence is presented. A tearing instability in a cylindrical plasma interacting with electrostatic drift waves is considered, for reasons of simplicity. Wave kinetics and adiabatic theory are used to treat the feedback of tearing mode flows on the drift waves via shearing and radial advection. The stresses exerted by the self-consistently evolved drift wave population density on the tearing mode are calculated by mean field methods. The principal effect of the drift waves is to pump the resonant low-m mode via a negative viscosity, consistent with the classical notion of an inverse cascade in quasi-two-dimensional turbulence. This process can occur alone or in synergy with current gradient drive of the low-m mode. Speculations of the relation of this multiscale process to the more general issue of the fate of energy transferred to large scales by an inverse cascade are presented. The existence of nonlinearly driven vortices pinned to low-q surfaces as a class of highly anisotropic dissipative structures which terminate the inverse cascade is proposed. The evolution of a finite size magnetic island is discussed.

Nonlinear Drive of Tearing Mode by Microscopic Plasma Turbulence

“…The case where the first term in the RHS of Eq. (42) is important has been discussed in, e.g., [18]. These findings illustrate the important roles of microscopic turbulence on the evolution of global perturbations, the integrated analyses of which require future intensive studies.…”

Interaction of turbulence with magnetic islands: effect on bootstrap current

“…Gyro-kinetic and fluid simulations [16,17,18,13,19] of the influence of large magnetic islands on driftwave instabilities and micro-scale turbulence have uncovered new physics. Furthermore recent analytic work has provided fresh insights into the multi-scale interaction of microinstabilities and large scale magnetic islands [20,8,21].…”

Excitation of macromagnetohydrodynamic mode due to multiscale interaction in a quasi-steady equilibrium formed by a balance between microturbulence and zonal flow

“…5 Effects of microturbulence on macro-MHD mode through nonlinear mode coupling are studied theoretically and numerically, and they are described by a negative eddy viscosity or by an anomalous resistivity. [8][9][10][11][12] On the other hand, the zonal flow caused by the turbulence can also affect the macro-MHD instability through the shearing of its radial structure. These effects of turbulence on macro-MHD should be simultaneously taken into account in numerical simulations.…”

“…[8][9][10][11][12] On the other hand, the zonal flow caused by the turbulence can also affect the macro-MHD instability through the shearing of its radial structure. These effects of turbulence on macro-MHD should be simultaneously taken into account in numerical simulations.…”