星系团中浮力气泡的三维磁流体动力学模拟
Three-dimensional Magnetohydrodynamic Simulations of Buoyant Bubbles in Galaxy Clusters
摘要：
本文报道了磁流体力学对磁化星系团介质中浮泡动力学的三维模拟结果。模拟是Jones & De Young（2005）报道的二维计算的三维扩展。最初的球形气泡和短暂膨胀的球形气泡，半径都比团内介质（ICM）尺度高度小几倍，随后，他们通过几个ICM尺度高度上升。这样的气泡迅速演变成一个环形的形式，在没有磁场的影响下，是稳定的，对我们的模拟分裂。这种环的形成是由于（常用的）初始条件导致气泡下方的ICM材料向上穿过气泡，产生涡环;也就是说，如果流体静力学气泡最初不是比ICM尺度高度小得多或大得多，那么它们就会发展成“烟圈”。即使是β = P_gas/P_mag ~ 10 ^3的适度ICM磁场也可以影响气泡的动力学，前提是磁场在与气泡大小相当或更小的尺度上没有纠缠。初始β值约为10^2的准均匀水平场会在气泡上升到ICM的高度之前将其一分为二，而弱得多的场会产生明显的扭曲。另一方面，具有类似的、适度强度的缠结磁场通常不太容易被气泡运动放大，因此对气泡演化的影响较小。在最初的气泡中包含一个非常强的、纠缠的磁场对我们的气泡演化几乎没有影响，因为这些磁场通过气泡的膨胀和初始磁场的重新连接而迅速减弱。
英文摘要：
We report results of 3D MHD simulations of the dynamics of buoyant bubbles in magnetized galaxy cluster media. The simulations are three dimensional extensions of two dimensional calculations reported by Jones & De Young (2005). Initially spherical bubbles and briefly inflated spherical bubbles all with radii a few times smaller than the intracluster medium (ICM) scale height were followed as they rose through several ICM scale heights. Such bubbles quickly evolve into a toroidal form that, in the absence of magnetic influences, is stable against fragmentation in our simulations. This ring formation results from (commonly used) initial conditions that cause ICM material below the bubbles to drive upwards through the bubble, creating a vortex ring; that is, hydrostatic bubbles develop into "smoke rings", if they are initially not very much smaller or very much larger than the ICM scale height. Even modest ICM magnetic fields with beta = P_gas/P_mag ~ 10^3 can influence the dynamics of the bubbles, provided the fields are not tangled on scales comparable to or smaller than the size of the bubbles. Quasi-uniform, horizontal fields with initial beta ~ 10^2 bifurcated our bubbles before they rose more than about a scale height of the ICM, and substantially weaker fields produced clear distortions. On the other hand, tangled magnetic fields with similar, modest strengths are generally less easily amplified by the bubble motions and are thus less influential in bubble evolution. Inclusion of a comparably strong, tangled magnetic field inside the initial bubbles had little effect on our bubble evolution, since those fields were quickly diminished through expansion of the bubble and reconnection of the initial field.
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。
