Intrinsic rotation driven by non-Maxwellian equilibria in tokamak plasmas

TL;DR

This paper investigates how small deviations from Maxwellian equilibrium, caused by diamagnetic effects, influence turbulent momentum transport in tokamaks, revealing a collisionality-dependent transition in intrinsic rotation profiles.

Contribution

It demonstrates that non-Maxwellian features significantly affect momentum flux and can explain the transition from peaked to hollow rotation profiles in tokamaks.

Findings

Radial momentum flux reverses direction with collisionality.

Transition from peaked to hollow rotation profiles observed.

Results align with experimental observations of intrinsic rotation.

Abstract

The effect of small deviations from a Maxwellian equilibrium on turbulent momentum transport in tokamak plasmas is considered. These non-Maxwellian features, arising from diamagnetic effects, introduce a strong dependence of the radial flux of co-current toroidal angular momentum on collisionality: As the plasma goes from nearly collisionless to weakly collisional, the flux reverses direction from radially inward to outward. This indicates a collisionality-dependent transition from peaked to hollow rotation profiles, consistent with experimental observations of intrinsic rotation.