Turbulent relaxation patterns in SOL plasma

TL;DR

This paper investigates how localized plasma over-density relaxes in the scrape-off layer, revealing the roles of drift-wave and interchange instabilities in shaping transport patterns and zonal flows.

Contribution

It provides a numerical analysis of the interplay between drift-wave and interchange instabilities in SOL plasma relaxation, highlighting their combined effects on transport.

Findings

Interchange instabilities cause low amplitude outward flux and zonal flows.

Drift-wave instabilities produce symmetric flux with large zonal flows.

Combined effects favor drift-waves, resulting in weaker outward flux and larger zonal flows.

Abstract

Relaxations of localized over-density in a plane transverse to the magnetic field are numericallyinvestigated under the effect of drift-wave and interchange drives in SOL conditions. Such a controlleddeparture from thermodynamic equilibrium allows the investigation of fundamental processesat play in cross-field transport. Interchange instabilities generate ballistic outward radial flux withlow amplitude zonal flow patterns, whereas drift-wave instabilities result in symmetric radial fluxwith large amplitude zonal flow patterns. When both instabilities are considered, the combinedeffects tend to favor drift-waves, leading to a weaker outward flux with larger zonal flow patterns.