Energy relaxation and the quasiequation of state of a dense two-temperature nonequilibrium plasma
Energy relaxation and the quasiequation of state of a dense two-temperature nonequilibrium plasma
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DOI：
10.1103/physreve.58.3705
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发表时间：
1998-09-01
影响因子：
2.4
通讯作者：
Perrot, F
中科院分区：
文献类型：
--
作者：
Dharma-wardana, MWC;Perrot, F
最近在《物理学》上提出了一种第一性原理方法来研究状态方程（EOS）和热力学平衡中电子、离子和中性相互作用混合物的输运性质。修订52,5352（1995）。然而，许多动态产生的等离子体具有不同于离子温度Ti的电子温度T-e。这些非平衡（非方程）系统的研究涉及(i)计算一个拟状态方程（拟eos）和所需的非方程。相关函数，如动态结构因子s -ss′（k, ω），其中s为物种指数；（ii）弛豫过程的计算。能量和动量弛豫通常用决定平衡速率的耦合常数来描述。这种耦合常数的简单斯皮策式计算通常使用通过平均介质对单个高能粒子的阻尼而得到的公式。然而，从换向子平均值[[H-e，H]-]计算电子分系统的能量损失率[dH(e)/dt]得到了不同的结果，其中H-e和H是电子分系统和整个系统的哈密顿量。这个结果对应于通过热系统的正常模式与冷系统的正常模式的相互作用的能量松弛。这种描述特别适合于致密等离子体。在费米黄金法则（FGR）或更复杂的Keldysh或Zubarev方法中对换向器平均值的评估，产生了涉及两个子系统动态结构因素的公式。单粒子方法和正模方法在概念上是非常不同的。在这里，我们给出了致密均匀双温铝等离子体的能量弛豫计算，并将通常的斯皮策型估计与我们更详细的fgr型结果进行了比较。我们的结果表明，弛豫率比常用理论给出的弛豫率小一个数量级以上。
A first principles approach to the equation of state (EOS) and the transport properties of an interacting mixture of electrons, ions, and neutrals in thermodynamic equilibrium was presented recently in Phys. Rev. E 52, 5352 (1995). However, many dynamically produced plasmas have an electron temperature T-e different from the ion temperature Ti. The study of these nonequilibrium (non-eq.) systems involves (i) calculation of a quasiequation of state (quasi-EOS) and the needed non-eq. correlation functions, e.g., the dynamic structure factors S-ss'(k, omega), where s is the species index; and (ii) a calculation of relaxation processes. The energy and momentum relaxations are usually described in terms of coupling constants determining the rates of equilibriation. Simple Spitzer-type calculations of such coupling constants often use formulas obtained by averaging the damping of a single energetic particle by the medium. However, a different result is obtained for the energy-loss rate [dH(e)/dt] of the electron subsystem when calculated from the commutator mean value [[H-e,H]-], where H-e and H are the Hamiltonians of the electron subsystem and the total system. This result corresponds to energy relaxation via the interaction of the normal modes of the hot system with the normal modes of the cold system. Such a description is particularly appropriate for dense plasmas. The evaluation of the commutator mean values within the Fermi golden rule (FGR), or more sophisticated Keldysh or Zubarev methods, yields formulations involving the dynamic structure factors of the two subsystems. The single-particle and normal-mode methods are conceptually very different. Here we present calculations of the energy relaxation of dense uniform two-temperature aluminum plasmas, and compare the usual Spitzer-type estimates with our more detailed FGR-type results. Our results show that the relaxation rate is more than an order of magnitude smaller than that given by the commonly used theories.