Galactic winds and the symmetry properties of galactic magnetic fields

¹ School of Mathematics, University of Manchester, Oxford Road, Manchester, M13 9PL, UK e-mail: moss@ma.man.ac.uk
² Department of Physics, Moscow University, 119 992 Moscow, Russia
³ Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany

Received: 20 October 2009
Accepted: 26 January 2010

Abstract

Context. Contemporary studies of the symmetry properties of galactic magnetic fields contain two contradictory ideas. There are observational and theoretical hints that large-scale magnetic fields are symmetric with respect to the galactic plane in the disc, and antisymmetric in the halo. On the other hand, standard galactic dynamo models without a galactic wind give symmetric or antisymmetric configurations in both disc and halo regions simultaneously.

Aims. Here we explore the role of a galactic wind in resolving this dichotomy.

Methods. The key idea is that a galactic wind must be be taken into account in order to resolve the problem. We perform a search of the parameter space of galactic dynamo models containing such winds.

Results. By including a galactic wind, magnetic configurations of such symmetry, i.e. approximately even in the disc and odd in the halo, can be obtained. We note that a variety of other solutions can also be found.

Conclusions. A galactic wind plays a significant role in determining the structure of galactic magnetic configurations and should be included in future modelling.