General Atomics, San Diego, California 92186-5608, USA.
Phys Rev Lett. 2011 Jun 10;106(23):235003. doi: 10.1103/PhysRevLett.106.235003.
In the standard δf theory of neoclassical transport, the zeroth-order (Maxwellian) solution is obtained analytically via the solution of a nonlinear equation. The first-order correction δf is subsequently computed as the solution of a linear, inhomogeneous equation that includes the linearized Fokker-Planck collision operator. This equation admits analytic solutions only in extreme asymptotic limits (banana, plateau, Pfirsch-Schlüter), and so must be solved numerically for realistic plasma parameters. Recently, numerical codes have appeared which attempt to compute the total distribution f more accurately than in the standard ordering by retaining some nonlinear terms related to finite-orbit width, while simultaneously reusing some form of the linearized collision operator. In this work we show that higher-order corrections to the distribution function may be unphysical if collisional nonlinearities are ignored.
在经典的新经典输运的 δf 理论中，零阶（麦克斯韦）解是通过求解非线性方程解析得到的。随后，将 δf 一阶修正作为一个包含线性化福克-普朗克碰撞算子的线性非齐次方程的解进行计算。这个方程仅在极端渐近极限（香蕉、高原、普菲歇尔-施吕特）下才有解析解，因此对于实际的等离子体参数必须进行数值求解。最近，出现了一些数值代码，它们试图通过保留一些与有限轨道宽度有关的非线性项，同时重新使用某种形式的线性化碰撞算子，比标准排序更准确地计算总分布函数 f。在这项工作中，我们表明如果忽略碰撞非线性，分布函数的高阶修正可能是不物理的。
