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 (T-e) gradient, the T-e turbulence, and the poloidal flow. The T-e gradient altered by the magnetic island steepens outside and flattens inside the island. The T-e turbulence can appear in increased T-e gradient regions. The combined effects of the Te gradient and the poloidal flow shear determines the two-dimensional distribution of the T-e turbulence. When the poloidal vortex flow forms, it can maintain the steepest T-e gradient and the magnetic island acts more like an electron heat transport barrier. Interestingly, when the T-e gradient, the T-e 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.