THE EFFECT OF ANISOTROPIC VISCOSITY ON COLD FRONTS IN GALAXY CLUSTERS
THE EFFECT OF ANISOTROPIC VISCOSITY ON COLD FRONTS IN GALAXY CLUSTERS
复制标题
各向异性粘度对星系团冷锋的影响
DOI：
10.1088/0004-637x/798/2/90
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
V. Biffi
中科院分区：
文献类型：
--
作者：
J. Zuhone;J. Zuhone;M. Kunz;M. Markevitch;James M. Stone;V. Biffi
冷锋--星系团内介质（ICM）中的接触不连续性--应该被开尔文-亥姆霍兹（K-H）不稳定性所破坏，这是由于相关的剪切速度。然而，许多观测到的冷锋似乎稳定。这开启了对稳定它们的微物理机制施加约束的可能性，例如ICM粘度和/或磁场。我们使用基于网格的Athena MHD代码对团簇核心中亚音速气体晃动产生的冷锋进行了探索性的高分辨率模拟，比较了各向同性Spitzer和各向异性Braginskii粘度（预期在磁化等离子体中）的影响。磁化模拟与全Braginskii粘度或各向同性Spitzer粘度减少了一个因素f 0.1都在定性与观察抑制K-H不稳定性。晃动区域内湍流的均方根速度仅因布拉金斯基粘度而略微降低。我们还进行了非磁化模拟和无粘性，发现磁场有显着的影响，冷锋的外观，即使初始场是弱的，粘度是相同的。这表明，从X射线观测中确定给定冷锋的主要抑制机制（例如，粘性或磁场）与模拟相比并不简单。最后，我们进行了模拟，包括各向异性热传导，并发现在这些模拟中，包括Braginskii粘度不会显着影响冷锋的演变，他们迅速涂抹的热传导，在无粘的情况下。
Cold fronts—contact discontinuities in the intracluster medium (ICM) of galaxy clusters—should be disrupted by Kelvin–Helmholtz (K-H) instabilities due to the associated shear velocity. However, many observed cold fronts appear stable. This opens the possibility of placing constraints on microphysical mechanisms that stabilize them, such as the ICM viscosity and/or magnetic fields. We performed exploratory high-resolution simulations of cold fronts arising from subsonic gas sloshing in cluster cores using the grid-based Athena MHD code, comparing the effects of isotropic Spitzer and anisotropic Braginskii viscosity (expected in a magnetized plasma). Magnetized simulations with full Braginskii viscosity or isotropic Spitzer viscosity reduced by a factor f ∼ 0.1 are both in qualitative agreement with observations in terms of suppressing K-H instabilities. The rms velocity of turbulence within the sloshing region is only modestly reduced by Braginskii viscosity. We also performed unmagnetized simulations with and without viscosity and find that magnetic fields have a substantial effect on the appearance of the cold fronts, even if the initial field is weak and the viscosity is the same. This suggests that determining the dominant suppression mechanism of a given cold front from X-ray observations (e.g., viscosity or magnetic fields) by comparison with simulations is not straightforward. Finally, we performed simulations including anisotropic thermal conduction, and find that including Braginskii viscosity in these simulations does not significantly affect the evolution of cold fronts; they are rapidly smeared out by thermal conduction, as in the inviscid case.
气体晃动、冷锋、开尔文·亥姆霍兹不稳定性和 Abell 496 星系团的合并历史
DOI：
10.1111/j.1365-2966.2011.20287.x
发表时间：
2012
影响因子：
4.8
作者：
Roediger;Lovisari;Ghizzardi;Brüggen;Machacek
通讯作者：
Machacek
化石簇气泡中的宇宙射线限制
DOI：
10.1111/j.1365-2966.2007.12659.x
发表时间：
2008
影响因子：
4.8
作者：
Ruszkowski;Enßlin;Brüggen;Begelman;Churazov
通讯作者：
Churazov