The Survival of Interstellar Clouds against Kelvin-Helmholtz Instabilities
The Survival of Interstellar Clouds against Kelvin-Helmholtz Instabilities
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DOI：
10.1086/304202
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发表时间：
1997-01
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影响因子：
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通讯作者：
M. Vietri;A. Ferrara;F. Miniati
中科院分区：
文献类型：
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作者：
M. Vietri;A. Ferrara;F. Miniati
我们考虑云的稳定性被一个更热的限制介质包围，相对于他们在运动，反对开尔文-亥姆霍兹不稳定性（KHIs）。在有冷却的情况下，声波因耗散而受到阻尼。当冷却时间短于声音穿越时间时，就像在正常的星际介质中一样，这意味着在两种介质的界面上产生的不稳定性不能传播到远离界面本身的地方。为了研究这对整体稳定性的影响，我们首先推导了被剪切层隔开的冷却介质的解析色散关系。耗散的加入并不能治愈不稳定性，但表明只有界面周围的小体积受到影响，微扰随距离表面的距离呈指数衰减；数值模拟证实了这一点。对球形云在周围云间介质中运动的数值模拟表明，这些云形成了一个核心/晕结构，其中一个是湍流晕，一个是层流核心，几乎没有受到khe的伤害。相关的和先前报道的“香槟效应”，即云似乎从顶部爆炸，通过包含辐射损失来治愈。
We consider the stability of clouds surrounded by a hotter confining medium with respect to which they are in motion, against Kelvin-Helmholtz instabilities (KHIs). In the presence of cooling, sound waves are damped by dissipation. Whenever cooling times are shorter than sound crossing times, as they are in the normal interstellar medium, this implies that the instability generated at the interface of the two media cannot propagate far from the interface itself. To study how this influences the overall stability, first we derive an analytic dispersion relation for cooling media, separated by a shear layer. The inclusion of dissipation does not heal the instability, but it is shown that only a small volume around the interface is affected, the perturbation decaying exponentially with distance from the surface; this is confirmed by numerical simulations. Numerical simulations of spherical clouds moving in a surrounding intercloud medium by which they are pressure confined show that these clouds develop a core/halo structure, with a turbulent halo, and a core in laminar flow nearly unscathed by the KHIs. The related and previously reported “champagne effect,” whereby clouds seem to explode from their top sides, is cured by the inclusion of radiative losses.