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Supernova-regulated ISM. V. Space and Time Correlations

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

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This is the authors' accepted manuscript of an article that has been published in its final definitive form by IOP Publishing, 2017.

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Abstract

We apply correlation analysis to random fields in numerical simulations of the supernova-driven interstellarmedium (ISM) with the magnetic field produced by dynamo action. We solve the thermomagnetohydrodynamic(MHD) equations in a shearing, Cartesian box representing a local region of the ISM,subject to thermal and kinetic energy injection by supernova explosions, and parameterized optically-thin radiativecooling. We consider the cold, warm and hot phases of the ISM separately; the analysis mostly considersthe warm gas, which occupies the bulk of the domain. Various physical variables have different correlationlengths in the warm phase: 40 pc, 50 pc, and 60 pc for random magnetic field, density, and velocity, respectively,in the midplane. The correlation time of the random velocity is comparable to the eddy turnover time,about 107 yr, although it may be shorter in regions with higher star formation rate. The random magnetic fieldis anisotropic, with the standard deviations of its components bx/by/bz having approximate ratios 0.5/0.6/0.6in the midplane. The anisotropy is attributed to the global velocity shear from galactic differential rotation, andlocally inhomogeneous outflow to the galactic halo. The correlation length of Faraday depth along the z-axis,120 pc, is greater than for electron density, 60–90 pc, and vertical magnetic field, 60 pc. Such comparisons maybe sensitive to the orientation of the line of sight. Uncertainties of the structure functions of synchrotron intensityrapidly increase with the scale. This feature is hidden in power spectrum analysis, which can underminethe usefulness of power spectra for detailed studies of interstellar turbulence


Publication metadata

Author(s): Hollins JF, Sarson GR, Shukurov A, Fletcher A, Gent FA

Publication type: Article

Publication status: Published

Journal: Astrophysical Journal

Year: 2017

Volume: 850

Issue: 1

Print publication date: 20/11/2017

Online publication date: 13/11/2017

Acceptance date: 14/10/2017

Date deposited: 18/10/2017

ISSN (print): 0004-637X

ISSN (electronic): 1538-4357

Publisher: IOP Publishing

URL: https://doi.org/10.3847/1538-4357/aa93e7

DOI: 10.3847/1538-4357/aa93e7


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