Statistics – Computation
Scientific paper
Apr 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994a%26a...284..731c&link_type=abstract
Astronomy and Astrophysics (ISSN 0004-6361), vol. 284, no. 3, p. 731-748
Statistics
Computation
22
Amplification, Astronomical Models, Barred Galaxies, Computational Astrophysics, Gas Flow, Interstellar Magnetic Fields, Spiral Galaxies, Velocity Distribution, Computation, Dynamo Theory, Gravitational Fields, Magnetohydrodynamics, Mathieu Function, Numerical Analysis, Perturbation Theory
Scientific paper
We present a magnetic-field amplification process in galaxies in conjunction with bar dynamics. Our model considers especially the observed non-circular gas velocities in barred spiral galaxies. The bar drives the spirally-falling gas flow toward the center, which consists of a net radial flow (referred to as flow b) and an elliptically elongated flow rotating in the azimuth (flow a). The induced radial flow by a bar (flow b) produces a magnetic field, whose exponential growth is closely related with the angular-momentum transport by the non-axisymmetric bar perturbation. Furthermore, the non-axisymmetric gas flow (flow a) also leads to the exponential and oscillatory growth of magnetic fields by driving a growing magnetic wave. The interplay of both flows in a bar hence induces an oscillatory amplification of magnetic fields, and the resulting magnetic field pattern rotates with a bar and holds the azimuthal wavenumber m = 1 or 2, depending on the strength of velocity disturbances. This model naturally explains the characteristic radio features observed in M83, where the m = 1 magnetic field is aligned with the bar, and the bar ends are dominated by the vertical component Bz, giving the holes in polarized intensity map. It is emphasized that the evolution of galactic magnetic fields is closely related with galactic dynamics and evolution.
Chiba Masashi
Lesch Harald
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