Three-dimensional Magnetohydrodynamic Simulations of Cold Fronts in Magnetically Turbulent ICM
Three-dimensional Magnetohydrodynamic Simulations of Cold Fronts in Magnetically Turbulent ICM
复制标题
DOI：
10.1086/518235
复制
发表时间：
2007-03
期刊：
影响因子：
--
通讯作者：
N. Asai;Naoya Fukuda;R. Matsumoto
中科院分区：
文献类型：
--
作者：
N. Asai;Naoya Fukuda;R. Matsumoto
钱德拉在穿过星系团内介质(ICM)的亚星系团的前沿观察到温度和密度的陡峭梯度，称为冷锋。冷锋的存在表明穿过冷锋的热传导受到磁场的抑制。我们进行了三维磁流体力学(MHD)模拟，包括亚星系团通过磁湍动ICM的各向异性热传导。我们发现，湍流磁场被沿子星系团和周围ICM之间的界面的剪切流拉伸和放大。由于磁场降低了锋面上的热传导效率，冷锋至少存活了1 Gyr。我们还发现，一个移动的子团簇起到了磁场放大器的作用。数值结果表明，伸展的湍流磁场在亚星系团后面积累，并因涡旋运动而进一步放大。移动子星团创建了有序磁场的长尾，其中磁场强度达到值β=pGAs/pMAG≲10。
Steep gradients of temperature and density, called cold fronts, are observed by Chandra in a leading edge of subclusters moving through the intracluster medium (ICM). The presence of cold fronts indicates that thermal conduction across the front is suppressed by magnetic fields. We carried out three-dimensional magnetohydrodynamic (MHD) simulations including anisotropic thermal conduction of a subcluster moving through a magnetically turbulent ICM. We found that turbulent magnetic fields are stretched and amplified by shear flows along the interface between the subcluster and the ambient ICM. Since magnetic fields reduce the efficiency of thermal conduction across the front, the cold front survives for at least 1 Gyr. We also found that a moving subcluster works as an amplifier of magnetic fields. Numerical results indicate that stretched turbulent magnetic fields accumulate behind the subcluster and are further amplified by vortex motions. The moving subcluster creates a long tail of ordered magnetic fields, in which the magnetic field strength attains a value of β = Pgas/Pmag ≲ 10.