Velocity–space structures of distribution function in toroidal ion temperature gradient turbulence
Velocity–space structures of distribution function in toroidal ion temperature gradient turbulence
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DOI：
10.1088/0029-5515/46/1/003
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发表时间：
2011-01
期刊：
影响因子：
3.3
通讯作者：
T. Watanabe;H. Sugama
中科院分区：
文献类型：
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作者：
T. Watanabe;H. Sugama
利用一个新开发的具有高速度空间分辨率的环形回旋动力学-Vlasov模拟程序，研究了离子温度梯度（ITG）湍流和带状流无碰撞阻尼作用下离子分布函数的速度空间结构.目前的模拟上的带状流和短程声学模式（GAM）成功地再现了新古典极化的囚禁离子以及弹道模式结构产生的碰撞粒子运动。在GAM的无碰撞阻尼过程中，速度空间中离子分布函数的精细尺度结构继续发展，同时保持由熵变量和势能之和定义的不变量。环向ITG湍流输运的模拟结果清楚地显示了分布函数精细速度空间结构的产生及其碰撞耗散。熵平衡的详细计算证实了湍流的统计稳定状态，其中反常输运平衡与耗散是由弱碰撞性给出的。通过高速度空间分辨率的模拟得到的上述结果也可以从相空间中熵变量的产生、传递和耗散过程的角度来理解。
Velocity–space structures of ion distribution function associated with the ion temperature gradient (ITG) turbulence and the collisionless damping of the zonal flow are investigated by means of a newly developed toroidal gyrokinetic-Vlasov simulation code with high velocity–space resolution. The present simulation on the zonal flow and the geodesic acoustic mode (GAM) successfully reproduces the neoclassical polarization of trapped ions as well as ballistic mode structures produced by collisionless particle motions. During the collisionless damping of GAM, the finer-scale structures of the ion distribution function in the velocity–space continue to develop while preserving an invariant defined by a sum of an entropy variable and the potential energy. The simulation results of the toroidal ITG turbulent transport clearly show generation of the fine velocity–space structures of the distribution function and their collisional dissipation. Detailed calculation of the entropy balance confirms the statistically steady state of turbulence, where the anomalous transport balances with the dissipation are given by the weak collisionality. The above results obtained by simulations with high velocity–space resolution are also understood in terms of generation, transfer and dissipation processes of the entropy variable in the phase–space.