Nonlinear dynamics of radiative condensations in optically thin plasmas
Nonlinear dynamics of radiative condensations in optically thin plasmas
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DOI：
10.1103/revmodphys.68.215
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发表时间：
1996
影响因子：
44.1
通讯作者：
B. Meerson
中科院分区：
文献类型：
--
作者：
B. Meerson
通过辐射冷却的等离子体可能变得不稳定，以形成较低温度和增加密度的局部区域。这种辐射凝聚在光学薄的天体物理和实验室等离子体中很常见。在简单模型的框架下，可以对辐射凝聚动力学的快速发展的理论理解给出一些看法。辐射凝结与热不稳定性的凝结模式密切相关，最早由G。B。领域最近取得的进展，在分析的非线性阶段，这种不稳定性，采用层次的时间和长度尺度的问题。简化方程组，它描述的辐射冷凝的非线性动力学，已分别在长，中，短波长的限制。作为完全不同的，所有这些简化模型预测辐射驱动的分离的不稳定等离子体成两个不同的状态（{open_quote}{open_quote}阶段{close_quote}{close_quote}）在一个中间的时间尺度。辐射凝结的后续长时间演化可能强烈依赖于等离子体边界条件的类型。如果允许等离子体的流入/流出，则辐射凝聚通常在较长的（与热传导相关的）时间尺度上消失。在这种情况下，其中一个"相“所占据的区域扩大，直到它们占据整个等离子体。相反，在受限的等离子体中（不允许等离子体的流入/流出），辐射凝聚可以“永远”存在。辐射凝聚和一些生长不稳定性之间的相似性已经被探索过，例如达里厄-朗道不稳定性和奥斯特瓦尔德熟化。本文描述了一种由辐射凝聚动力学引起的具有非单调压力分布的新型激波。简要讨论了磁场在辐射凝聚中的作用。«少
Plasmas that cool by radiation may become unstable to the formation of localized regions of lower temperature and increased density. Such radiative condensations are common in astrophysical and laboratory plasmas that are optically thin. Some perspective of the rapidly developing theoretical understanding of the dynamics of radiative condensations can be given in the framework of simple models. Radiative condensations are closely related to the condensation mode of the thermal instability, first studied by G. B. Field. Progress in the analysis of the nonlinear stage of this instability, achieved recently, employs the hierarchy of time and length scales of the problem. Sets of reduced equations, which describe the nonlinear dynamics of the radiative condensation, have been developed separately in the long-, intermediate-, and short-wavelength limits. Being quite different, all these reduced models predict radiation-driven segregation of the unstable plasma into two different states ({open_quote}{open_quote}phases{close_quote}{close_quote}) on an intermediate time scale. Subsequent long-time evolution of radiative condensation may strongly depend on the type of boundary condition for the plasma. Radiative condensations usually disappear on a longer (thermal conduction related) time scale, if an inflow/outflow of the plasma is allowed. In this case, regions occupied by one of the ``phases`` expand until they occupymore » the whole plasma. On the contrary, in confined plasmas (no inflow/outflow of the plasma is allowed), radiative condensations can persist ``forever``. Similarities have been explored between radiative condensations and a number of instabilities of growth, such as the Darrieus-Landau instability and Ostwald ripening. A new type of shock wave with a nonmonotonic pressure profile, resulting from radiative condensation dynamics, is described. The role of magnetic fields in radiative condensations is briefly discussed.« less