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

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 an 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 observations such as turbulence spreading into an MI and turbulence enhancement at the reconnection site, elucidating intricate effects of plasma turbulence on the nonlinear MI evolution.

Localized compressional self-heating in magnetic islands

“…It follows that the finding of heating inside an induced magnetic island, in Choi et al. (2021), might be linked to the heating mechanism described in this paper. The absence of background turbulence in the simulations shown did not allow us to observe the propagation of the fluctuations to the -point as described in the experiment (Choi et al.…”

“…2021) and some instances of experimental observations of magnetic islands with non-flat pressure profile or localized heating (Choi et al. 2021). The mainstream experimental approach of using the modified Rutherford equation to predict the saturation of magnetic islands (Escande & Ottaviani 2004; Militello & Porcelli 2004) has been shown to have limited validity (Ishizawa & Nakajima 2010; Borgogno et al.…”

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

“…The synchronized enhancement of the bicoherence with the RMP field penetration in the ELM suppression phase and its strong anti-correlation with the rescaled complexity imply that the coupling among the fluctuations is via a resonant island at the pedestal top. Indeed, the three-wave coupling among the turbulence via an island was already observed in the initial phase of the neoclassical tearing mode [24].…”

“…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.…”