The supernova-regulated ISM - II. The mean magnetic field
The supernova-regulated ISM - II. The mean magnetic field
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DOI：
10.1093/mnrasl/sls042
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发表时间：
2012-06
影响因子：
4.8
通讯作者：
F. Gent;A. Shukurov;G. Sarson;A. Fletcher;M. Mantere
中科院分区：
文献类型：
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作者：
F. Gent;A. Shukurov;G. Sarson;A. Fletcher;M. Mantere
采用三维非理想可压缩磁流体动力学模拟方法研究了旋涡星系星际介质中磁场的起源和结构，包括星系重力场的分层、差异旋转和辐射冷却。一个矩形区域，大小为1 × 1 × 2 kpc 3，横跨银河系中面的两侧。超新星爆炸驱动跨音速湍流。种子磁场呈指数增长，在1.6 Gyr内达到统计稳定状态。在Germano（1992）之后，我们使用具有高斯核的体积平均来将磁场分离为平均场和波动。这样的平均并不满足所有的雷诺法则，但允许平均场理论的公式化。这样得到的平均场在空间和时间上都是变化的。平均场和波动场的增长率不同，两个元素之间有明显的尺度分离，其积分尺度分别约为0.7和0.3千秒差距。
The origin and structure of the magnetic fields in the interstellar medium of spiral galaxies is investigated with 3D, non-ideal, compressible magnetohydrodynamic simulations, including stratification in the galactic gravity field, differential rotation and radiative cooling. A rectangular domain, 1 × 1 × 2 kpc 3 in size, spans both sides of the galactic mid-plane. Supernova explosions drive transonic turbulence. A seed magnetic field grows exponentially to reach a statistically steady state within 1.6 Gyr. Following Germano (1992), we use volume averaging with a Gaussian kernel to separate magnetic field into a mean field and fluctuations. Such averaging does not satisfy all Reynolds rules, yet allows a formulation of mean-field theory. The mean field thus obtained varies in both space and time. Growth rates differ for the meanfield and fluctuating field and there is clear scale separation between the two elements, whose integral scales are about 0.7 and 0.3 kpc, respectively.