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The Parker instability in disk galaxies

Lookup NU author(s): Dr Luiz Felippe RodriguesORCiD, Dr Graeme Sarson, Professor Anvar ShukurovORCiD, Professor Paul BushbyORCiD, Dr Andrew Fletcher



This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License (CC BY-NC 4.0).


We examine the evolution of the Parker instability in galactic disks using 3D numerical simulations. We consider a local Cartesian box section of a galactic disk, where gas, magnetic fields, and cosmic rays are all initially in a magnetohydrostatic equilibrium. This is done for different choices of initial cosmic-ray density and magnetic field. The growth rates and characteristic scales obtained from the models, as well as their dependences on the density of cosmic rays and magnetic fields, are in broad agreement with previous (linearized, ideal) analytical work. However, this nonideal instability develops a multimodal 3D structure, which cannot be quantitatively predicted from the earlier linearized studies. This 3D signature of the instability will be of importance in interpreting observations. As a preliminary step toward such interpretations, we calculate synthetic polarized intensity and Faraday rotation measure (RM) maps, and the associated structure functions of the latter, from our simulations; these suggest that the correlation scales inferred from RM maps are a possible probe for the cosmic-ray content of a given galaxy. Our calculations highlight the importance of cosmic rays in these measures, making them an essential ingredient of realistic models of the interstellar medium.

Publication metadata

Author(s): Rodrigues LFS, Sarson GR, Shukurov A, Bushby PJ, Fletcher A

Publication type: Article

Publication status: Published

Journal: The Astrophysical Journal

Year: 2016

Volume: 816

Issue: 1

Print publication date: 01/01/2016

Online publication date: 21/12/2015

Acceptance date: 05/11/2015

Date deposited: 10/02/2016

ISSN (print): 0004-637X

ISSN (electronic): 1538-4357

Publisher: IOP


DOI: 10.3847/0004-637X/816/1/2


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Funder referenceFunder name
N8 consortium
PIRSES-GA-2010-269264European Commission
PRG-2014-427Leverhulme Trust