Magnetic Spiral Arms in Galaxy Halos

Abstract

We seek the conditions for a {\it steady} mean field galactic dynamo. The parameter set is reduced to those appearing in the ${\alpha }^2$ and $\alpha /\omega$ dynamo, namely velocity amplitudes, and the ratio of sub-scale helicity to diffusivity. The parameters can be allowed to vary on conical spirals. We analyze the mean field dynamo equations in terms of scale invariant logarithmic spiral modes and special exact solutions. Compatible scale invariant gravitational spiral arms are introduced and illustrated in an appendix, but the detailed dynamical interaction with the magnetic field is left for another work. As a result of planar magnetic spirals `lifting' into the halo, multiple sign changes in average rotation measures forming a regular pattern on each side of the galactic minor axis, are predicted. Such changes have recently been detected in the CHANG-ES survey.

arXiv comment44 double-spaced pages, 10 figures plus 1 appendix figure, accepted to MNRAS

References in corpus (8)

• Magnetic Fields in Spiral Galaxies
• CHANG-ES IV: Radio continuum emission of 35 edge-on galaxies observed with the Karl G. Jansky Very Large Array in D-configuration, Data Release 1
• Magnetic fields in the nearby spiral galaxy IC 342: A multi-frequency radio polarization study
• Non-linear galactic dynamos: A toolbox
• The relation between magnetic and material arms in models for spiral galaxies
• Magnetized galactic halos and velocity lags
• Spiral Structure in Scale-free, Thin Discs: Rigid Rotation
• Steady Galactic Dynamos and Observational Consequences I: Halo Magnetic Fields

Cited by in corpus (13)

• CHANG-ES XV: Large-scale magnetic field reversals in the radio halo of NGC 4631
• CHANG-ES XXI. Transport processes and the X-shaped magnetic field of NGC 4217: off-center superbubble structure
• CHANG-ES XIX: Galaxy NGC 4013 -- a diffusion-dominated radio halo with plane-parallel disk and vertical halo magnetic fields
• Exact axially symmetric galactic dynamos
• Evolving Galactic Dynamos and Fits to the Reversing Rotation Measures in the Halo of NGC 4631
• The origin of the structure of large-scale magnetic fields in disc galaxies
• Helicity in the Large-Scale Galactic Magnetic Field
• An underlying universal pattern in galaxy halo magnetic fields
• Galactic magnetic X fields
• Influence of Magnetic Fields on the Gas Rotation in the Galaxy $NGC6946$
• A three-dimensional model for the reversal in the local large-scale interstellar magnetic field
• Turbulent Magnetic Dynamos with Halo Lags, Winds, and Jets
• Synthesizing Observations and Theory to Understand Galactic Magnetic Fields: Progress and Challenges