Localized modulation of turbulence by m/n  =  1/1 magnetic islands in the HL-2A tokamak

Abstract

Modulation of turbulent electron temperature fluctuations () and density fluctuations () by an m/n = 1/1 tearing mode island was observed in the core plasma region of the HL-2A tokamak. High spatiotemporal resolution two-dimensional images of show the first evidence that the turbulence modulation occurs only when the island width exceeds a certain threshold value ( cm) and the modulation is localized merely in the inner area of the island due to significant alteration of local profiles and turbulence drives. Evidence also reveals that for large islands turbulence spreading takes place across the island region. The results are generally consistent with theories and simulations.

Interaction of magnetic islands with turbulent electron temperature fluctuations in DIII-D and in GENE nonlinear gyrokinetic simulations

“…Possible concomitant transient changes in T e can there-fore be studied across growing islands in non-equilibrium conditions, in contrast to saturated islands. T e modifications by saturated islands has been reported earlier 29,30 .…”

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

“…In other words, this turbulence outside an MI can spread into the MI if its amplitude is sufficiently large 30 . In the recent DIII-D 31 and HL-2A 32 experiments 12 , 33 , 34 , observations which seem to result from the spreading of the density and temperature turbulence towards the O-point of an MI are reported. In addition, the nonlinear electrostatic gyrokinetic simulation based on the KSTAR plasma equilibrium and profiles showed that turbulence and the heat can spread into an MI which was initially stable region 35 .…”

“…This implies that the turbulent transport around an MI can be also modified, meaning that the evolution of plasma turbulence and the evolution of the MI are coupled. However, there has been relatively little experimental research progress 7 , 9 , 11 , 12 in addressing the effects of plasma turbulence on the MI evolution to date.…”

Stochastic fluctuation and transport of tokamak edge plasmas with the resonant magnetic perturbation field

“…Recently, the interaction between an island and turbulence has been extensively studied [25,26]. Their interactions are known to result in coupled evolution between an island and turbulence [27,28,29,30,24]. Turbulence can be modified by the island associated change of the background pressure [31,32] and flow [33,34,35,36,37,38] profiles [39], which in turn affects the evolution of the island [27,28,29,30,24].…”

“…Their interactions are known to result in coupled evolution between an island and turbulence [27,28,29,30,24]. Turbulence can be modified by the island associated change of the background pressure [31,32] and flow [33,34,35,36,37,38] profiles [39], which in turn affects the evolution of the island [27,28,29,30,24]. Understanding the formation and evolution of the stochastic layer in the pedestal region should also require considering intricate turbulence effects.…”