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arXiv · 1206.6784

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

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

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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F. A. Gent, A. Shukurov, A. Fletcher, G. R. Sarson, M. J. Mantere. 2012-11-28. The supernova-regulated ISM. II. The mean magnetic field. https://doi.org/10.1093/mnrasl%2Fsls042

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