托卡马克边缘湍流中带状流的负粘滞阻尼

Negative viscosity damping of zonal flows in tokamak edge turbulence

基于Hasegawa-Wakatani湍流模型,数值模拟了托卡马克边缘等离子体中漂移波湍流和相关的反常粒子输运。从等离子体动量守恒方程出发导出了不采用常规的布辛涅斯克近似的带状流方程,论证了大振幅密度扰动和湍性粒子流对激发带状流的贡献可等效地对应于低阶负粘滞阻尼效果。数值模拟表明,大振幅密度扰动的非线性大大增强了带状流饱和振幅,从而有效抑制了湍性粒子输运。研究结果阐明了托卡马克边缘等离子体大振幅密度扰动的非线性对驱动等离子体旋转、动量输运和带状流的重要性。

Drift wave turbulence and associated particle transport are simulated based on Hasegawa- Wakatani turbulence model in tokamak edge plasmas. A zonal flow equation without assuming conventional Boussinesq approximation is derived from the plasma momentum conservation. Meanwhile, it is justified that the contribution of the large-amplitude density fluctuation as well as the turbulent particle flux to the zonal flow dynamics may be effectively equivalent to a low-order negative viscosity damping. Simulations show that the nonlinearity of large-amplitude density fluctuation can greatly enhance the zonal flow saturated amplitude, so that turbulent particle transport is dramatically suppressed. The results elucidate the importance of the nonlinearity of large-amplitude density fluctuation in driving plasma rotation, momentum transport and zonal flow generation in tokamak edge plasmas.