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

Lookup NU author(s): Fred Gent, Professor Anvar Shukurov, Dr Graeme Sarson, Dr Andrew Fletcher

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Abstract

The origin and structure of the magnetic fields in the interstellar medium of spiral galaxies isinvestigated with 3D, non-ideal, compressible magnetohydrodynamic simulations, includingstratification in the galactic gravity field, differential rotation and radiative cooling. A rectan-gular domain, 1×1×2 kpc3 in size, spans both sides of the galactic mid-plane. Supernovaexplosions drive transonic turbulence. A seed magnetic field grows exponentially to reach astatistically steady state within 1.6 Gyr. Following Germano (1992), we use volume averagingwith a Gaussian kernel to separate magnetic field into a mean field and fluctuations. Suchaveraging 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, whoseintegral scales are about 0.7 and 0.3 kpc, respectively.


Publication metadata

Author(s): Gent FA, Shukurov A, Sarson GR, Fletcher A, Mantere MJ

Publication type: Letter

Publication status: Published

Journal: Monthly Notices of the Royal Astronomical Society

Year: 2013

Volume: 430

Issue: 1

Pages: L40-L44

Print publication date: 23/12/2013

ISSN (electronic): 1745-3933

Publisher: Oxford University Press

URL: http://dx.doi.org/10.1093/mnrasl/sls042

DOI: 10.1093/mnrasl/sls042


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