Galactic magnetic X fields
arXiv:2112.09023 · doi:10.1051/0004-6361/202142330
Abstract
Our aim in this note is to compare a recent explanation of the galactic X pattern in Faraday Rotation (XRM), to that produced by the advection part of the classical dynamo.We find that the characteristic X magnetic field polarization in the plane of the sky, found in edge-on spiral galaxies, can develop magnetohydromagnetically from an initial disc magnetic field combined with wind and rotation. The Rotation Measure develops a corresponding X distribution in sign, but this distribution is not a `universal' behaviour because it depends primarily on the velocity field. We use Cauchy evolution of an initial magnetic field to find the field at some later time and place. A `battery' mechanism that requires current to always flow out of a galaxy has been recently suggested, which contrasts with the conclusions of this paper. Either explanation has significant consequences for the structure of a spiral galaxy. If the battery mechanism applies then we have a new method of producing magnetic field independent of the traditional dynamo. If however the flow mechanism applies; then constraints concerning the presence and nature of a galactic wind, together with the signature of the mean radial magnetic field, can be inferred.
arXiv comment6 pages four figures; accepted December 9,2021
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Cited by in corpus (3)
- CHANG-ES XXXIV: Magnetic Field Structure in Edge-On Galaxies Characterising large-scale magnetic fields in galactic halos
- CHANG-ES XXXVII. Effects of spectral aging on radio scale heights
- Magnetohydrodynamic turbulence and the associated spatial diffusion tensor of cosmic rays in dynamical galactic halos