Tracing the Pathway from Drift-Wave Turbulence with Broken Symmetry to the Generation of Sheared Axial Mean Flow

TL;DR

This paper demonstrates how drift-wave turbulence with broken symmetry in a plasma can generate sheared axial flows through Reynolds stress, linking density gradients, turbulence, and flow in a causal manner.

Contribution

It provides the first direct evidence of the causal pathway from density gradient-induced turbulence to sheared axial flow in a plasma device.

Findings

Reynolds stress develops with steepening density profiles

Non-diffusive Reynolds stress driven by spectral asymmetry

Causal link established between density gradient, turbulence, and flow

Abstract

This study traces the emergence of sheared axial flow from collisional drift wave turbulence with broken symmetry in a linear plasma device---CSDX. As the density profile steepens, the axial Reynolds stress develops and drives a radially sheared axial flow that is parallel to the magnetic field. Results show that the non-diffusive piece of the Reynolds stress is driven by the density gradient and results from the spectral asymmetry of the turbulence and thus is dynamical in origin. Taken together, these findings constitute the first simultaneous demonstration of the causal link between the density gradient, turbulence and stress with broken spectral symmetry, and the mean axial flow.