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

Abstract

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 assumptions and predictions are satisfied. Key results include (1) a sensitivity of the nonlinear zonal flow response to the energy content of the linear instability, (2) a persistence of zonal-flow-regulated saturation at high temperature gradients, (3) a physical explanation of the nonlinear saturation process in terms of secondary and tertiary instabilities, and (4) dependence of heat flux in terms of dimensionless parameters.

Final journal version. Some clarifications and a new Fig. 4

References in corpus (5)

• Nonlinear entropy transfer via zonal flows in gyrokinetic plasma turbulence
• Collisionless microinstabilities in stellarators III - the ion-temperature-gradient mode
• The energetic coupling of scales in gyrokinetic plasma turbulence
• Considering Fluctuation Energy as a Measure of Gyrokinetic Turbulence
• Gyrokinetic simulation of entropy cascade in two-dimensional electrostatic turbulence

Cited by in corpus (8)

• Phase mixing vs. nonlinear advection in drift-kinetic plasma turbulence
• Distinct turbulence saturation regimes in stellarators
• Simple advecting structures and the edge of chaos in subcritical tokamak plasmas
• A Flux-Balanced Fluid Model for Collisional Plasma Edge Turbulence: Numerical Simulations with Different Aspect Ratios
• The residual flow in well-optimized stellarators
• On the nonlinear stability of a quasi-two-dimensional drift kinetic model for ion temperature gradient turbulence
• Hidden drifts in turbulence
• Exploring zonal flow mediated saturation on stellarators