Effects of plasma turbulence on the nonlinear evolution of magnetic island in tokamak

TL;DR

This paper investigates how plasma turbulence influences the nonlinear evolution of magnetic islands in tokamak plasmas, revealing that turbulence can both stabilize and destabilize these structures, affecting plasma stability.

Contribution

It provides the first comprehensive two-dimensional experimental observations of turbulence effects on magnetic island evolution in tokamaks.

Findings

Turbulence can destabilize or stabilize magnetic islands.

Enhanced turbulence at the X-point triggers rapid magnetic reconnection.

Turbulence influences magnetic field stochastization and plasma disruption.

Abstract

Magnetic islands (MIs), resulting from a magnetic field reconnection, are ubiquitous structures in magnetized plasmas. In tokamak plasmas, recent researches suggested that the interaction between the MI and ambient turbulence can be important for the nonlinear MI evolution, but a lack of detailed experimental observations and analyses has prevented further understanding. Here, we provide comprehensive two-dimensional observations that indicate various effects of the ambient turbulence on the nonlinear MI evolution. It is shown that the modified plasma turbulence around the MI can lead to either destabilization or stabilization of the MI instability in tokamak plasmas. In particular, significantly enhanced turbulence at the X-point of the MI results in a violent disruption through the fast magnetic reconnection and magnetic field stochastization.