CHEMISTRY IN DIFFUSE CLOUDS WITH TRANSIENT MICROSTRUCTURE
CHEMISTRY IN DIFFUSE CLOUDS WITH TRANSIENT MICROSTRUCTURE
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具有瞬态微观结构的弥散云中的化学
DOI：
10.1088/0004-637x/706/2/1429
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
S. Casu
中科院分区：
文献类型：
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作者：
C. Cecchi;D. Williams;S. Viti;S. Casu
在弥漫的星际介质中，可以在许多视线上观察到微观结构，主要是通过十年或更短时间尺度上原子线吸收的变化。这个时间尺度意味着微观结构的大小与太阳系相当。它是超压且短暂的。观察和理论都证实微观结构中存在特定的化学反应。因此，我们探索了一种弥漫星际气体的模型，其中弥漫云中的化学物质由许多瞬态和微小扰动中的化学物质补充。这里假设这些扰动的来源不明，但假设它们内部发生双极扩散。对于合理的物理参数，我们发现该模型可以解释在扩散云中观察到的分子柱密度范围，包括传统模型通常无法解释的物种。一些分子离子预计会在微观结构中产生（包括 HS+、CH+2、CH+3、H2O+ 和 H3O+），但尚未在弥漫云中观察到，但其存在水平应该可以检测到。
Microstructure is observed on many lines of sight in the diffuse interstellar medium, mainly through variations in atomic line absorptions on timescales of a decade or less. This timescale implies that microstructure exists on a size scale comparable with that of the solar system; it is overpressured and transient. Both observations and theory confirm that a specific chemistry occurs in microstructure. We therefore explore a model of diffuse interstellar gas in which the chemistry in diffuse clouds is supplemented by chemistry in many transient and tiny perturbations. These perturbations are here assumed to be of unidentified origin, but it is assumed that ambipolar diffusion occurs within them. For plausible physical parameters, we find that this model can account for the range of molecular column densities observed in diffuse clouds, including species not usually accounted for by conventional models. Some molecular ions, predicted to be generated in the microstructure (including HS+, CH+2, CH+3, H2O+, and H3O+) but not yet observed in diffuse clouds, should be present at levels that may allow their detection.