Numerical study of zonal flow dynamics and electron transport in electron temperature gradient driven turbulence
Numerical study of zonal flow dynamics and electron transport in electron temperature gradient driven turbulence
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DOI：
10.1063/1.1669397
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发表时间：
2004-04-01
影响因子：
2.2
通讯作者：
Kishimoto, Y
中科院分区：
文献类型：
--
作者：
Li, JQ;Kishimoto, Y
基于具有绝热离子响应的三维回旋流体模型，对电子温度梯度（ETG）驱动的托卡马克核心等离子体湍流进行了数值研究。重点讨论了ETG波动中的纬向流动动力学和由此产生的电子热输运。在弱磁剪切区发现了一个高电子能量约束模式，这与湍流的自组织行为有关，通过增强的纬向流动动力学而不是ETG波动的弱剪切稳定。结果表明，弱切变有利于ETG湍流中纬向流动的增强。从湍流波动的空间谱分析和时频小波分析中可以看出，纬向流动的增强可能受到二次Kelvin-Helmholtz模态的激发的限制。电磁ETG模拟表明，虽然在中等剪切等离子体中再现了chi(e)与1/beta(e)成比例的异常电子输移的Ohkawa标度，但在弱剪切ETG湍流中，由于磁Reynolds应力产生的纬向流减少，有限的β效应可能逆转了Ohkawa标度。此外，环面耦合增强了纬向流动，同时破坏了ETG模态的稳定性。因此，在弱剪切等离子体中，由于复杂的不稳定和稳定竞争，电子传递似乎对环向度不敏感。(C) 2004年美国物理研究所。
The electron temperature gradient (ETG) driven turbulence in tokamak core plasmas is numerically investigated based on a three-dimensional gyrofluid model with adiabatic ion response. Attentions are focused on the zonal flow dynamics in ETG fluctuations and the resultant electron heat transport. A high electron energy confinement mode is found in the weak magnetic shear region, which is relevant to the self-organization behavior of turbulence through the enhanced zonal flow dynamics rather than the weak shear stabilization of ETG fluctuations. It is demonstrated that the weak shear favors the enhancement of zonal flows in ETG turbulence. The enhanced zonal flows may be plausibly limited by the excitation of a secondary Kelvin-Helmholtz mode, which is observed from the spatial spectral analyses and time-frequency wavelet analyses of turbulent fluctuations. Electromagnetic ETG simulations show that while the Ohkawa's scaling of anomalous electron transport with beta, chi(e) proportional to 1/beta(e), is reproduced in the moderate shear plasma, the finite beta effect may reverse the Ohkawa's scaling in weak shear ETG turbulence due to the reduction of zonal flow generation by the magnetic Reynolds stress. Further, it is shown that the toroidal coupling enhances the zonal flow while it destabilizes the ETG mode. Hence, the electron transport seems insensitive to the toroidicity in the weak shear plasma due to the complex destabilizing and stabilizing competitions. (C) 2004 American Institute of Physics.