UBIQUITOUS NON-THERMALS IN ASTROPHYSICAL PLASMAS: RESTATING THE DIFFICULTY OF MAINTAINING MAXWELLIANS
UBIQUITOUS NON-THERMALS IN ASTROPHYSICAL PLASMAS: RESTATING THE DIFFICULTY OF MAINTAINING MAXWELLIANS
复制标题
天体物理等离子体中普遍存在的非热力：重申维持麦克斯韦方程组的困难
DOI：
--
复制
发表时间：
2013
期刊：
影响因子：
--
通讯作者：
H. Karimabadi
中科院分区：
文献类型：
--
作者：
J. Scudder;H. Karimabadi
本文概述了辐射去耦合等离子体的较窄的条件，其中麦克斯韦-玻尔兹曼(MB)分布可以很有把握地假定。具有非微扰峰度的互补非热分布被认为具有比以前所接受的更广泛的范围。这些条件用电子努森数Ke表示，Ke是电子平均自由程与电子压强标度长度之比。更一般地，f(v<；v2(Ke))将是高斯的，因此由速度v<；v2≡w(15/8KE)1/4控制的MB原子或波粒子效应将保持可防御，其中w是最可能的速度。能量方程下斯皮策-布拉金斯基等离子体流体闭合的充分条件要求Ke(S)⩽为0.0 1；这个整体条件与Ke沿磁场(到其末端)的弧长S的最大值有关，前提是连续的等离子体与辐射场保持不耦合。非热区KE>；0.01在距地表约0.05恒星半径以上的所有主序恒星大气中都很常见。整个日冕和风都被包括在这个区域中，非热分布的峰度是普遍存在的，热通量不能很好地用Spitzer-Braginskii闭合来模拟，流体模拟充其量是定性的。
This paper outlines the rather narrow conditions on a radiatively decoupled plasma where a Maxwell–Boltzmann (MB) distribution can be assumed with confidence. The complementary non-thermal distribution with non-perturbative kurtosis is argued to have a much broader purview than has previously been accepted. These conditions are expressed in terms of the electron Knudsen number, Ke, the ratio of the electron mean free path to the scale length of electron pressure. Rather generally, f(v < v2(Ke)) will be Gaussian, so that MB atomic or wave particle effects controlled by speeds v < v2 ≡ w(15/8Ke)1/4 will remain defensible, where w is the most probable speed. The sufficient condition for Spitzer–Braginskii plasma fluid closure at the energy equation requires globally Ke(s) ⩽ 0.01; this global condition pertains to the maximum value of Ke along the arc length s of the magnetic field (to its extremities) provided that contiguous plasma remains uncoupled from the radiation field. The non-thermal regime Ke > 0.01 is common in all main-sequence stellar atmospheres above approximately 0.05 stellar radii from the surface. The entire solar corona and wind are included in this regime where non-thermal distributions with kurtosis are shown to be ubiquitous, heat flux is not well modeled by Spitzer–Braginskii closure, and fluid modeling is qualitative at best.