Vorticity and intrinsic ambipolarity in turbulent tokamaks
Vorticity and intrinsic ambipolarity in turbulent tokamaks
复制标题
湍流托卡马克中的涡度和内在双极性
DOI：
10.1088/0741-3335/51/9/095008
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发表时间：
2009
影响因子：
2.2
通讯作者：
P. Catto
中科院分区：
文献类型：
--
作者：
F. Parra;P. Catto
传统的静电陀螺动力学处理包括陀螺动力学的福克-普朗克方程和陀螺动力学的准中性方程。在一些简化情况下，这两个方程都可以在宏观长度展开的陀螺半径上找到二阶方程，但在代码中实现的版本通常只有一阶。在轴对称结构中，如托卡马克，计算分布函数的精度不足以确定新经典径向电场。此外，我们在这里证明了湍流主导的托卡马克本质上是双极性的，正如新古典托卡马克一样。因此，传统的陀螺动力学描述不能正确计算环面旋转，从而不能正确计算轴对称径向电场。我们研究了在旋动力状态下，波长为离子拉莫尔半径数量级的涡度方程∇·J = 0。我们明确地表明，如果要从准中性中恢复径向电场，陀螺动力学需要在陀螺半径展开中至少计算到三阶。研究涡度方程的方法也提出了一种解决问题的方法，即用一个旋动力涡度方程来代替准中性方程。这里导出的涡度方程只得到所需的通量函数内的势。
Traditional electrostatic gyrokinetic treatments consist of a gyrokinetic Fokker–Planck equation and a gyrokinetic quasineutrality equation. Both of these equations can be found up to second order in a gyroradius over macroscopic length expansion in some simplified cases, but the versions implemented in codes are typically only first order. In axisymmetric configurations such as the tokamak, the accuracy to which the distribution function is calculated is insufficient to determine the neoclassical radial electric field. Moreover, we prove here that turbulence dominated tokamaks are intrinsically ambipolar, as are neoclassical tokamaks. Therefore, traditional gyrokinetic descriptions are unable to correctly calculate the toroidal rotation and hence the axisymmetric radial electric field. We study the vorticity equation, ∇ · J = 0, in the gyrokinetic regime, with wavelengths on the order of the ion Larmor radius. We explicitly show that gyrokinetics needs to be calculated at least to third order in the gyroradius expansion if the radial electric field is to be retrieved from quasineutrality. The method employed to study the vorticity equation also suggests a solution to the problem, namely, solving a gyrokinetic vorticity equation instead of the quasineutrality equation. The vorticity equations derived here only obtain the potential within a flux function as required.