The supernova-regulated ISM. II. The mean magnetic field
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.
Keywords
Cite
@article{arxiv.1206.6784,
title = {The supernova-regulated ISM. II. The mean magnetic field},
author = {F. A. Gent and A. Shukurov and A. Fletcher and G. R. Sarson and M. J. Mantere},
journal= {arXiv preprint arXiv:1206.6784},
year = {2013}
}
Comments
5 pages, 10 figures, submitted to Monthly Notices Letters