Limitations of gyrokinetics on transport time scales
Limitations of gyrokinetics on transport time scales
复制标题
回旋运动学对传输时间尺度的限制
DOI：
10.1088/0741-3335/50/6/065014
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发表时间：
2008
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
本文提出了一种新的递推方法，可以求出在磁场特征长度上的回转半径展开式中一阶正确的全f静电回转运动方程。这一过程为回转动力学准中性方程的局限性提供了新的见解。我们发现，为了自洽地计算静电势的长波分量，离子分布函数必须在特征长度的回转半径中至少已知到二阶。此外，利用稳态θ-Pinch的例子，我们证明了即使具有二阶正确的分布函数，准中性方程也不能提供位势的轴对称部分。我们还证明，如果用更方便的力矩方程来代替准中立性方程，二阶精度就足够了。这些结果表明，如果要在分析中保留长波分量，回转运动的准中性方程不是求静电势的最有效的方法。
We present a new recursive procedure to find a full f electrostatic gyrokinetic equation correct to first order in an expansion of gyroradius over magnetic field characteristic length. The procedure provides new insights into the limitations of the gyrokinetic quasineutrality equation. We find that the ion distribution function must be known at least to second order in gyroradius over characteristic length to calculate the long wavelength components of the electrostatic potential self-consistently. Moreover, using the example of a steady-state θ-pinch, we prove that the quasineutrality equation fails to provide the axisymmetric piece of the potential even with a distribution function correct to second order. We also show that second order accuracy is enough if a more convenient moment equation is used instead of the quasineutrality equation. These results indicate that the gyrokinetic quasineutrality equation is not the most effective procedure to find the electrostatic potential if the long wavelength components are to be retained in the analysis.