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arXiv 1401.2629astro-ph.HE
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平行面超爱丁顿大气中辐射流体动力学不稳定性:团簇形成的一种机制

Radiation Hydrodynamic Instability in Plane-Parallel, Super-Eddington Atmosphere: A Mechanism for Clump Formation

S. Takeuchi, K. Ohsuga, S. Mineshige

摘要:

为了了解超临界吸积流外流中团块形成的物理过程,我们进行了二维辐射流体动力学(RHD)模拟。我们集中讨论的性质,RHD的不稳定性在轻微的光学厚,平面平行,超爱丁顿大气。最初,我们设置两层大气的密度对比度为100,暴露于强大的,向上的连续辐射力;较低的一层比上一个,RHD不稳定的条件下密度。我们假设引力不为零,但与辐射力相比可以忽略不计。我们发现,短波长的扰动首先增长,然后增长的较长波长的图案,这导致形成的cluximetric结构。团块(云)的典型大小对应于大约一个光学深度。辐射压力和气体压力之间的反相关性被确认:这种反相关性提供了一个阻尼机制的波长较长的扰动比典型的团块大小。物质和辐射能量密度是相关的。这些特征正是我们在超临界流出的辐射-磁流体动力学(辐射-MHD)模拟中发现的。

英文摘要:

In order to understand the physical processes underlying clump formation in outflow from supercritical accretion flow, we performed two-dimensional radiation hydrodynamic (RHD) simulations. We focus our discussion on the nature of RHD instability in marginally optically thick, plane-parallel, super-Eddington atmosphere. Initially we set two-layered atmosphere with a density contrast of 100 exposed to strong, upward continuum-radiation force; the lower layer is denser than the upper one, condition for an RHD instability. We assume non-zero but negligible gravitational force, compared with the radiation force. We find that short wavelength perturbations first grow, followed by growth of longer wavelength patterns, which lead to the formation of clumpy structure. The typical size of clumps (clouds) corresponds to about one optical depth. An anti-correlation between the radiation pressure and the gas pressure is confirmed: this anti-correlation provides a damping mechanism of longer wavelength perturbations than the typical clump size. Matter and radiation energy densities are correlated. These features are exactly what we found in the radiation-magnetohydrodynamic (radiation-MHD) simulations of supercritical outflow.

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