# Multiscale interaction between a large scale magnetic island and small scale turbulence

## TL;DR

This study demonstrates the complex multiscale interactions between magnetic islands and turbulence, revealing how they influence electron heat transport and can lead to disruptions in plasma confinement.

## Contribution

It provides the first detailed measurement-based analysis of the coupled dynamics between magnetic islands and turbulence at multiple scales.

## Key findings

- Magnetic islands modify the electron temperature gradient distribution.
- T_e turbulence correlates with regions of increased T_e gradient.
- Critical levels of gradient, turbulence, and flow shear can trigger rapid heat transport and disruptions.

## Abstract

Multiscale interaction between the magnetic island and turbulence has been demonstrated through simultaneous two-dimensional measurements of turbulence and temperature and flow profiles. The magnetic island and turbulence mutually interact via the coupling between the electron temperature ($T_e$) gradient, the $T_e$ turbulence, and the poloidal flow. The $T_e$ gradient altered by the magnetic island is peaked outside and flattened inside the island. The $T_e$ turbulence can appear in the increased $T_e$ gradient regions. The combined effects of the $T_e$ gradient and the the poloidal flow shear determine two-dimensional distribution of the $T_e$ turbulence. When the reversed poloidal flow forms, it can maintain the steepest $T_e$ gradient and the magnetic island acts more like a electron heat transport barrier. Interestingly, when the $T_e$ gradient, the $T_e$ turbulence, and the flow shear increase beyond critical levels, the magnetic island turns into a fast electron heat transport channel, which directly leads to the minor disruption.