Galactic halo bubble magnetic fields and UHECR deflections

Abstract

We consider the synchrotron emission from electrons out in the Galactic halo bubble region where the Fermi bubble structures reside. Utilising a simple analytical expression for the non-thermal electron distribution and a toy magnetic field model, we simulate polarised synchrotron emission maps at a frequency of 30~GHz. Comparing these maps with observational data, we obtain constraints on the parameters of our toy Galactic halo bubble magnetic field model. Utilising this parameter value range for the toy magnetic field model, we determine the corresponding range of arrival directions and suppression factors of ultra high energy cosmic rays (UHECRs) from potential local source locations. We find that high levels of flux suppression (down to 2\%) and large deflection angles ($\ge 80^{\circ }$) are possible for source locations whose line-of-sight pass through the Galactic halo bubble region. We conclude that the magnetic field out in the Galactic halo bubble region can strongly dominate the level of deflection UHECRs experience whilst propagating from local sources to Earth.

13 pages, 4 figures + 5 Appendix figures

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Cited by in corpus (5)

• The coherent magnetic field of the Milky Way halo, Local Bubble and Fan Region
• Differences Between the Pierre Auger Observatory and Telescope Array Spectra: Systematic Effects or Indication of a Local Source of Ultra-High-Energy Cosmic Rays?
• UHECR Echoes from the Council of Giants
• The Huge Magnetic Toroids in the Milky Way Halo
• The role of magnetic fields in shaping $\gamma$-ray emission from the Fermi bubbles