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Simulations of Galactic Dynamos

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Magnetic Fields in Diffuse Media

Part of the book series: Astrophysics and Space Science Library ((ASSL,volume 407))

Abstract

We review our current understanding of galactic dynamo theory, paying particular attention to numerical simulations both of the mean-field equations and the original three-dimensional equations relevant to describing the magnetic field evolution for a turbulent flow. We emphasize the theoretical difficulties in explaining non-axisymmetric magnetic fields in galaxies and discuss the observational basis for such results in terms of rotation measure analysis. Next, we discuss nonlinear theory, the role of magnetic helicity conservation and magnetic helicity fluxes. This leads to the possibility that galactic magnetic fields may be bi-helical, with opposite signs of helicity and large and small length scales. We discuss their observational signatures and close by discussing the possibilities of explaining the origin of primordial magnetic fields.

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Acknowledgements

I am indebted to Oliver Gressel and Kandaswamy Subramanian for reading the manuscript and providing help and useful comments. Financial support from the European Research Council under the AstroDyn Research Project 227952, the Swedish Research Council under the grants 621-2011-5076 and 2012-5797, as well as the Research Council of Norway under the FRINATEK grant 231444 are gratefully acknowledged.

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  1. Nordic Institute for Theoretical Physics, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, 10691, Stockholm, Sweden

    Axel Brandenburg

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  1. Department of Astronomy, University of Wisconsin-Madison, Madison, Wisconsin, USA

    Alexander Lazarian

  2. Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, São Paulo, Brazil

    Elisabete M. de Gouveia Dal Pino

  3. Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, São Paulo, Brazil

    Claudio Melioli

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Brandenburg, A. (2015). Simulations of Galactic Dynamos. In: Lazarian, A., de Gouveia Dal Pino, E., Melioli, C. (eds) Magnetic Fields in Diffuse Media. Astrophysics and Space Science Library, vol 407. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-662-44625-6_19

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