Intrinsic rotation driven by turbulent acceleration

Abstract

Differential rotation is induced in tokamak plasmas when an underlying symmetry of the governing gyrokinetic-Maxwell system of equations is broken. One such symmetry-breaking mechanism is considered here: the turbulent acceleration of particles along the mean magnetic field. This effect, often referred to as the 'parallel nonlinearity', has been implemented in the δf gyrokinetic code stella and used to study the dependence of turbulent momentum transport on the plasma size and on the strength of the turbulence drive. For JET-like parameters with a wide range of driving temperature gradients, the momentum transport induced by the inclusion of turbulent acceleration is similar to or smaller than the ratio of the ion Larmor radius to the plasma minor radius. This low level of momentum transport is explained by demonstrating an additional symmetry that prohibits momentum transport when the turbulence is driven far above marginal stability.

Isotope effects on intrinsic rotation in hydrogen, deuterium and tritium plasmas

“…Most theories for intrinsic rotation attribute the observed rotation to a turbulent redistribution of momentum within the plasma core. Several effects have been invoked to explain this turbulent redistribution [27][28][29][30][31][32][33]. For a preliminary analysis of the data, we focus on one of the drives, namely the effect of neoclassical parallel velocity and heat flow on the turbulence [27].…”

A novel approach to radially global gyrokinetic simulation using the flux-tube code $\texttt{stella}$

“…It is worthwhile to point out that most global gyrokinetic codes do not retain all higher order terms in ρ * , e.g., diamagnetic flows[27,28,29,30] and the parallel nonlinearity[31,32,33,34,35] …”