Astronomy and Astrophysics – Astrophysics
Scientific paper
Jan 1996
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996a%26a...305..114z&link_type=abstract
Astronomy and Astrophysics, v.305, p.114
Astronomy and Astrophysics
Astrophysics
14
Magnetohydrodynamics, Ism: Supernova Remnants, Magnetic Fields, Turbulence
Scientific paper
We calculate all components of the dynamo alpha-tensor produced by supernova explosions in the galactic disk. In our turbulence model, we numerically simulate only isolated explosions, taking into account galactic differential rotation but neglecting Lorentz forces. From the time-dependent 3-dimensional magnetohydrodynamic (MHD) simulations, the turbulent electromotive force (EMF) is calculated and then averaged over an empirical supernova distribution function to derive the α-tensor for a field of explosions. We simulate explosions occurring in the solar neighborhood (8.5kpc) and at a radius of 3kpc from the galactic center. According to the specific physical conditions of the interstellar medium (ISM) at these galactocentric radii, we found components of the α-tensor, α_ij_, which differ in their spatial profiles perpendicular to the disk and their amplitudes. Our results, based upon numerical experiments, generally confirm the analytic results given by Ferriere (1992a,b). The exact values of the amplitudes strongly depend on the scale height of the supernova distribution. Generally, we find α-values of only a few meters per second. The component α_yx_ is shown to represent an effective vertical velocity at which gas and the confined magnetic flux escape from the galactic plane. The amplitude of α_yx_ is about two orders of magnitude larger than the other non-negligible α-components. This is a serious problem since horizontal magnetic flux is advected away from the galactic disk with much higher rate than can be regenerated through α-action.
Kaisig Michael
Yorke Harold W.
Ziegler Udo
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