论文标题
孤立星系中银河发电机的数值依赖性
Numerical dependencies of the galactic dynamo in isolated galaxies with SPH
论文作者
论文摘要
了解对银河发电机作用的数值依赖性是确定正确捕获星系中观察到的磁场所需的分辨率和条件的关键步骤。在这里，我们提出了一项关于使用平滑的颗粒磁流体动力学（SPMHD）在分离的螺旋星系中银河发电机在分离的螺旋星系中的数值依赖性的广泛研究。我们进行了53个孤立的螺旋星系模拟，具有不同的初始设置，反馈，分辨率，牛仔裤地板和耗散参数。结果表明，在磁盘的螺旋臂区域中发生了强大的平均电场发电机，这可能是由经典的α-欧洲式发电机或最近描述的引力不稳定性发电机产生的。反馈的包括在放大过程中以破坏性和积极的方式起作用。由于磁盘中细丝结构的分解，湍流扩散的增加以及从中央平面到圆形循环介质的磁通量的弹射而发生的破坏性干扰是由于细丝结构的分解而发生的。反馈的积极作用是垂直运动的增加和发展的湍流喷泉流，显示出对小规模垂直结构和银河系中的数值耗散的高度依赖。具有有效发电机的星系在热能密度的10-30％之间使其磁能密度饱和。对于我们所有的模拟，在整个星系中，密度平均的数值prandtl数值低于统一，而半径的值则增加。假设湍流注入长度为1 kpc，数值磁性雷诺数在$ re_ {mag} = 10-400 $的范围内，这表明某些区域低于小规模发电机所需的水平（$ re_ {mag {mag，crit，crit} = 30-2700 $）才能活跃。
Understanding the numerical dependencies that act on the galactic dynamo is a crucial step in determining what resolution and what conditions are required to properly capture the magnetic fields observed in galaxies. Here, we present an extensive study on the numerical dependencies of the galactic dynamo in isolated spiral galaxies using smoothed particle magnetohydrodynamics (SPMHD). We performed 53 isolated spiral galaxy simulations with different initial setups, feedback, resolution, Jeans floor and dissipation parameters. The results show a strong mean-field dynamo occurring in the spiral-arm region of the disk, likely produced by the classical alpha-omega dynamo or the recently described gravitational instability dynamo. The inclusion of feedback is seen to work in both a destructive and positive fashion for the amplification process. Destructive interference for the amplification occurs due to break down of filament structure in the disk, increase of turbulent diffusion and the ejection of magnetic flux from the central plane to the circumgalactic medium. The positive effect of feedback is the increase in vertical motions and the turbulent fountain flows that develop, showing a high dependence on the small-scale vertical structure and the numerical dissipation within the galaxy. Galaxies with an effective dynamo saturate their magnetic energy density at levels between 10-30% of the thermal energy density. The density averaged numerical Prandtl number is found to be below unity throughout the galaxy for all our simulations, with an increasing value with radius. Assuming a turbulent injection length of 1 kpc, the numerical magnetic Reynolds number are within the range of $Re_{mag}=10-400$, indicating that some regions are below the levels required for the small-scale dynamo ($Re_{mag,crit}=30-2700$) to be active.
