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Magnetic Reconnection and Extraplanar Diffuse Ionized Gas

Published online by Cambridge University Press:  12 April 2016

Guido T. Birk
Affiliation:
Institut für Astronomie und Astrophysik, LMU München, Scheinerstr. 1, 81679 München, Germany
Harald Lesch
Affiliation:
Institut für Astronomie und Astrophysik, LMU München, Scheinerstr. 1, 81679 München, Germany
Thomas Neukirch
Affiliation:
School of Mathematical and Computational Sciences, University of St. Andrews, St. Andrews, Fife KY16 9SS, Scotland, United Kingdom

Abstract

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Many observations indicate the occurrence of ionized gas in the distant halos of galaxies (among them our own). Since photoionization by stars (mainly O stars, young or evolved low mass stars depending on the kind of galaxy) does not seem to be exclusively responsible for the ionization of the hydrogen filaments that should otherwise cool and recombine quickly, the question arises which energy source may result in the quasistationary ionization. We propose that localized magnetic field dissipation in current filaments may contribute to the ionization of the extraplanar halo gas. The dissipated magnetic energy is converted into heat, which then is transferred to the neutrals, resulting in re-ionization on a time scale shorter than the recombination time scale. Quasistatic solutions are characterized by plasma temperatures and densities that agree nicely with the observed values for the diffuse ionized gas component of the Galactic interstellar medium.

Type
Part IX External Galaxies
Copyright
Copyright © Springer-Verlag 1998

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