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Galactic spiral patterns and dynamo action

Published online by Cambridge University Press:  18 July 2013

Luke Chamandy ,
Kandaswamy Subramanian  and
Anvar Shukurov
Luke Chamandy
Affiliation:
Inter-University Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune 411007, India
Kandaswamy Subramanian
Affiliation:
Inter-University Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune 411007, India
Anvar Shukurov
Affiliation:
School of Mathematics & Statistics, Newcastle University, Newcastle upon Tyne NE1 7RU, United Kingdom
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Abstract

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The theory of mean-field galactic dynamos is generalized by allowing for a finite response time of the mean electromotive force (emf) to variations in the mean magnetic field and small-scale turbulence. A non-axisymmetric forcing of the dynamo by a spiral pattern (either stationary or transient) is invoked. The resulting magnetic spiral arms are phase-shifted from the spiral arms of the pattern by an angle 15°–40°, opposite to the sense of galactic rotation. Our findings may help to explain the phase shift between material and magnetic arms observed in NGC 6946 and other galaxies.

Keywords

magnetic fields – MHD – galaxies: magnetic fields – galaxies: spiral

References

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