Supernovae driven turbulence in the interstellar medium
Supernovae driven turbulence in the interstellar medium
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超新星驱动星际介质中的湍流
DOI：
10.10443/1755
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
F. Gent
中科院分区：
文献类型：
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作者：
F. Gent
我用重力、微分旋转和其他我们认为是典型的太阳邻居的参数来模拟被超新星随机加热和冲击的多相星际介质（ISM）。模拟是三维的，水平扩展1 x 1 kpc平方，垂直扩展2 kpc，对称于银河系中平面。它们通常跨越每立方厘米1/10000到100的气体密度，温度100到100 MK，速度高达10000公里/秒，马赫数高达25。辐射冷却应用于两种广泛采用的参数化，并直接比较以评估结果对冷却的敏感性。有强有力的证据表明，ISM由定义明确的冷区、暖区和热区组成，这些区域在统计上接近热和总压平衡。这个结果对这里所考虑的参数的选择不敏感。气体密度的分布可以用对数正态分布进行鲁棒建模。在超新星活动的中间平面内的气体的性质和这个区域以外的更均匀的相之间需要适当的区别。阐明了相体积分数与其各种指标之间的联系。然后推导出分数体积和根据体积和概率平均值定义的填充因子之间的精确关系。这些结果在观测和计算两方面进行了讨论。随机流的相关尺度由速度自相关函数计算；它的数量级为100pc，并且随着距离中平面的距离而增长。在非理想MHD模拟中研究了ISM中磁场的来源和结构。一个体积平均约为4ng的种子磁场呈指数增长，在1.6 Gyr内达到统计稳定状态。
I model the multi-phase interstellar medium (ISM) randomly heated and shocked by supernovae, with gravity, differential rotation and other parameters we understand to be typical of the solar neighbourhood. The simulations are 3D extending horizontally 1 x 1 kpc squared and vertically 2 kpc, symmetric about the galactic mid-plane. They routinely span gas number densities 1/10000 to 100 per cubic cm, temperatures 100 to 100 MK, speeds up to 10000 km/s and Mach number up to 25. Radiative cooling is applied from two widely adopted parameterizations, and compared directly to assess the sensitivity of the results to cooling. There is strong evidence to describe the ISM as comprising well defined cold, warm and hot regions, which are statistically close to thermal and total pressure equilibrium. This result is not sensitive to the choice of parameters considered here. The distribution of the gas density within each can be robustly modelled as lognormal. Appropriate distinction is required between the properties of the gases in the supernova active mid-plane and the more homogeneous phases outside this region. The connection between the fractional volume of a phase and its various proxies is clarified. An exact relation is then derived between the fractional volume and the filling factors defined in terms of the volume and probabilistic averages. These results are discussed in both observational and computational contexts. The correlation scale of the random flows is calculated from the velocity autocorrelation function; it is of order 100 pc and tends to grow with distance from the mid-plane. The origin and structure of the magnetic fields in the ISM is also investigated in non-ideal MHD simulations. A seed magnetic field, with volume average of roughly 4 nG, grows exponentially to reach a statistically steady state within 1.6 Gyr.