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arXiv 0704.3592astro-ph
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包括热传导的流动热等离子体中星际云的演化

The evolution of interstellar clouds in a streaming hot plasma including heat conduction

W. Vieser, G. Hensler

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19 pages, 12 figures, accepted in Astronomy and Astrophysics
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摘要：

为了研究热等离子体流中巨型分子云的演化，我们进行了二维流体动力学模拟，充分考虑了自引力，加热和冷却效应以及电子热传导。我们使用Spitzer提出的完全电离的氢等离子体的热导率和Cowie & McKee提出的饱和热通量，在电子的平均自由程比温度scaleheight大的区域。显着的结构和进化的差异之间发生的模拟和没有热传导。在纯动力学模式中，稠密云经历开尔文-亥姆霍兹（KH）不稳定性的动力学破坏。在静态模型中，热传导导致这种云的蒸发。作用在气流中的云上的热传导消除了云边缘陡峭的温度和密度梯度，因为传导时间尺度比冷却时间尺度短。这减小了流动等离子体和云之间的速度梯度，因此KH不稳定性开始的时间尺度增加，云的表面变得不太容易受到KH不稳定性的影响。热传导对KH不稳定性的稳定作用对于较小和质量较小的云更为明显。在静态情况下，更现实的云条件允许热传导将热物质转移到云的表面，并将吸积气体混合到云的更深处。

英文摘要：

To examine the evolution of giant molecular clouds in the stream of a hot plasma we performed two-dimensional hydrodynamical simulations that take full account of self-gravity, heating and cooling effects and heat conduction by electrons. We use the thermal conductivity of a fully ionized hydrogen plasma proposed by Spitzer and a saturated heat flux according to Cowie & McKee in regions where the mean free path of the electrons is large compared to the temperature scaleheight. Significant structural and evolutionary differences occur between simulations with and without heat conduction. Dense clouds in pure dynamical models experience dynamical destruction by Kelvin-Helmholtz (KH) instability. In static models heat conduction leads to evaporation of such clouds. Heat conduction acting on clouds in a gas stream smooths out steep temperature and density gradients at the edge of the cloud because the conduction timescale is shorter than the cooling timescale. This diminishes the velocity gradient between the streaming plasma and the cloud, so that the timescale for the onset of KH instabilities increases, and the surface of the cloud becomes less susceptible to KH instabilities. The stabilisation effect of heat conduction against KH instability is more pronounced for smaller and less massive clouds. As in the static case more realistic cloud conditions allow heat conduction to transfer hot material onto the cloud's surface and to mix the accreted gas deeper into the cloud.

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