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arXiv 1206.6784astro-ph.GAastro-ph.SR
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超新星调节的ISM。II。平均磁场

The supernova-regulated ISM. II. The mean magnetic field

F. A. Gent, A. Shukurov, A. Fletcher, G. R. Sarson, M. J. Mantere

摘要:

利用三维非理想可压缩MHD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。一个大小为1x 1x 2 kpc^{3}的矩形区域横跨银河系中面的两侧。超新星爆炸驱动跨音速湍流。种子磁场以指数方式增长以在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成平均场和波动。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。平均场和涨落场的增长率不同,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 kpc和0.3 kpc。

英文摘要:

The origin and structure of the magnetic fields in the interstellar medium of spiral galaxies is investigated with 3D, non-ideal, compressible MHD simulations, including stratification in the galactic gravity field, differential rotation and radiative cooling. A rectangular domain, 1x1x2 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 mean-field and fluctuating field and there is clear scale separation between the two elements, whose integral scales are about 0.7 kpc and 0.3 kpc, respectively.

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