Coherent structures in ion temperature gradient turbulence-zonal flow

Coherent structures in ion temperature gradient turbulence-zonal flow

Zonal flow generation in ion temperature gradient mode turbulence

In the present work the zonal flow ~ZF! growth rate in toroidal ion-temperature-gradient ~ITG! mode turbulence including the effects of elongation is studied analytically. The scaling of the ZF growth with plasma parameters is examined for typical tokamak parameter values. The physical model used for the toroidal ITG driven mode is based on the ion continuity and ion temperature equations where...

Fine-Scale Zonal Flow Suppression of Electron Temperature Gradient Turbulence

Abstract. It is found in collisionless Electron Temperature Gradient (ETG) turbulence simulations that, while zonal flows are weak at early times, the zonal flows continue to grow algebraically (proportional to time). These fine-scale zonal flows have a radial wave number such that krρi > 1 and krρe < 1. Eventually, the zonal flows grow to a level that suppresses the turbulence due to ExB shear...

Understanding nonlinear saturation in zonal-flow-dominated ion temperature gradient turbulence

We propose a quantitative model of ion temperature gradient driven turbulence in toroidal magnetized plasmas. In this model, the turbulence is regulated by zonal flows, i.e. mode saturation occurs by a zonal-flow-mediated energy cascade (‘shearing’), and zonal flow amplitude is controlled by nonlinear decay. Our model is tested in detail against numerical simulations to confirm that both its as...

Coherent structure phenomena in drift wave-zonal flow turbulence

Zonal flows are azimuthally symmetric plasma potential perturbations spontaneously generated from small-scale drift-wave fluctuations via the action of Reynolds stresses. We show that, after initial linear growth, zonal flows can undergo further nonlinear evolution leading to the formation of long-lived coherent structures which consist of self-bound wave packets supporting stationary shear lay...