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

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 can mutually interact via coupling between the electron temperature (Te) gradient, the Te turbulence, and the poloidal flow. The Te gradient altered by the magnetic island steepens outside and flattens inside the island. The Te turbulence can appear in increased Te gradient regions. The combined effects of the Te gradient and the poloidal flow shear determines the two-dimensional distribution of the Te turbulence. When the poloidal vortex flow forms, it can maintain the steepest Te gradient and the magnetic island acts more like an electron heat transport barrier. Interestingly, when the Te gradient, the Te turbulence, and the vortex flow shear increase beyond critical levels, the magnetic island turns into a fast electron heat transport channel, which directly leads to the minor disruption.