Annu. Rev. Astron. Astrophys. 1996. 34: 155-206
Copyright © 1996 by . All rights reserved

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GALACTIC MAGNETISM: Recent Developments and Perspectives

Rainer Beck

Max Planck Institute for Radioastronomy, Auf dem Hügel 69, Bonn, D-53121 Germany

Axel Brandenburg ¹

Nordita, Blegdamsvej 17, Copenhagen Ø, DK-2100 Denmark

David Moss

Mathematics Department, The University, Manchester M13 9PL, United Kingdom

Anvar Shukurov

Computing Center, Moscow University, Moscow, 119899 Russia

Dmitry Sokoloff
Department of Physics, Moscow University, Moscow, 119899 Russia

Abstract. We discuss current observational and theoretical knowledge of magnetic fields, especially the large-scale structure in the disks and halos of spiral galaxies. Among other topics, we consider the enhancement of global magnetic fields in the interarm regions, magnetic spiral arms, and representations as superpositions of azimuthal modes, emphasizing a number of unresolved questions. It is argued that a turbulent hydromagnetic dynamo of some kind and an inverse cascade of magnetic energy gives the most plausible explanation for the regular galactic magnetic fields. Primordial theory is found to be unsatisfactory, and fields of cosmological origin may not even be able to provide a seed field for a dynamo. Although dynamo theory has its own problems, the general form of the dynamo equations appears quite robust. Finally, detailed models of magnetic field generation in galaxies, allowing for factors such as spiral structure, starbursts, galactic winds, and fountains, are discussed and confronted with observations.

KEY WORDS: radio syncrotron emission, radio polarization, spiral arms, galactic halos, dynamos

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