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arXiv 1503.04509astro-ph.HEastro-ph.GA
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考虑cosmic-ray扩散效应的磁转动不稳定性分析

Analysis of the magneto-rotational instability with the effect of cosmic-ray diffusion

Takuhito Kuwabara, Chung-Ming Ko

摘要:

我们提出了从线性稳定性分析和2.5维磁流体动力学(MHD)模拟的磁旋转不稳定性(MRI),包括宇宙射线(CR)的影响。我们考虑了CR沿磁场的扩散,但忽略了跨场线的扩散。本文考虑了两种模型:剪切箱模型和差动旋转圆柱模型。我们研究了MRI如何受到初始CR压力的影响(即,能量)分布。在剪切箱模型中,初始状态为均匀分布。线性分析表明,MRI的增长率不依赖于CR扩散系数的值。在差动旋转圆柱体模型中,初始状态是一个由弱均匀垂直磁场穿过的常角动量多变圆盘。线性分析表明,CR扩散系数越大,MRI的增长率越大。这两个结果都得到了MHD模拟的证实。MHD模拟结果表明,物质的向外运动的增长的MRI是不受CR压力梯度,离心力的作用,集中的物质变得更大。因此,MRI的增长率增加。另一方面,如果初始CR压力是均匀的,则MRI的生长速率几乎不依赖于CR扩散系数的值。

英文摘要:

We present the results obtained from linear stability analysis and 2.5-dimensional magnetohydrodynamic (MHD) simulations of the magnetorotational instability (MRI), including the effects of cosmic rays (CRs). We took into account of the CR diffusion along the magnetic field but neglect the cross-field-line diffusion. Two models are considered in this paper: shearing box model and differentially rotating cylinder model. We studied how MRI is affected by the initial CR pressure (i.e., energy) distribution. In the shearing box model, the initial state is uniform distribution. Linear analysis shows that the growth rate of MRI does not depend on the value of CR diffusion coefficient. In the differentially rotating cylinder model, the initial state is a constant angular momentum polytropic disk threaded by weak uniform vertical magnetic field. Linear analysis shows that the growth rate of MRI becomes larger if the CR diffusion coefficient is larger. Both results are confirmed by MHD simulations. The MHD simulation results show that the outward movement of matter by the growth of MRI is not impeded by the CR pressure gradient, and the centrifugal force which acts to the concentrated matter becomes larger. Consequently, the growth rate of MRI is increased. On the other hand, if the initial CR pressure is uniform, then the growth rate of the MRI barely depends on the value of the CR diffusion coefficient.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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