Influence of plasma background on 3D scrape-off layer filaments

TL;DR

This study investigates how plasma-neutral interactions and plasma background conditions affect the behavior and velocity of 3D scrape-off layer filaments, revealing dependencies on temperature, density, and filament size.

Contribution

It introduces a self-consistent model including plasma-neutral interactions to analyze filament dynamics, highlighting the influence of plasma viscosity and background conditions on filament velocity and size.

Findings

Filament velocity increases with upstream electron temperature.

Filament velocity decreases with increasing electron density.

Critical filament size shifts with plasma density due to viscosity effects.

Abstract

This paper presents the effect of self-consistent plasma backgrounds including plasma-neutral interactions, on the dynamics of filament propagation. The principle focus is on the influence of the neutrals on the filament through both direct interactions and through their influence on the plasma background. Both direct and indirect interactions influence the motion of filaments. A monotonic increase of filament peak velocity with upstream electron temperature is observed, while a decrease with increasing electron density is observed. If ordered by the target temperature, the density dependence disappears and the filament velocity is only a function of the target temperature. Smaller filaments keep a density dependence, as a result of the density dependence of the plasma viscosity. The critical size $\delta^*$, where filaments are fastest, is shifted to larger sizes for higher densities, due to the plasma viscosity. If the density dependence of the plasma viscosity is removed, $\delta^*$ has no temperature dependence, but rather a density dependence.