Lookup NU author(s): Amit Seta,
Professor Anvar Shukurov,
Dr Toby Wood,
Dr Paul Bushby,
Dr Andrew Snodin
This is the authors' accepted manuscript of an article that has been published in its final definitive form by Oxford University Press, 2018.
For re-use rights please refer to the publisher's terms and conditions.
Synchrotron radiation from cosmic rays is a key observational probe of the galactic magneticfield. Interpreting synchrotron emission data requires knowledge of the cosmic ray number density, which is often assumed to be in energy equipartition (or otherwise tightly correlated) with the magnetic field energy. However, there is no compelling observational or theoretical reason to expect such tight correlation to hold across all scales. We use test particle simulations, tracing the propagation of charged particles (protons) through a random magnetic field, to study the cosmic ray distribution at scales comparable to the correlation scale of the turbulent flow in the interstellar medium (approx 100 pc in spiral galaxies). In these simulations, we find that there is no spatial correlation between the cosmic ray number density and the magnetic field energy density. In fact, their distributions are approximately statistically independent. We find that low-energy cosmic rays can become trapped between magnetic mirrors, whose location depends more on the structure of the field lines than on the field strength.
Author(s): Seta A, Shukurov A, Wood TS, Bushby PJ, Snodin AP
Publication type: Article
Publication status: Published
Journal: Monthly Notices of the Royal Astronomical Society
Print publication date: 01/02/2018
Online publication date: 09/10/2017
Acceptance date: 04/10/2017
ISSN (print): 0035-8711
ISSN (electronic): 1365-2966
Publisher: Oxford University Press
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