Magnetic fields in the Galactic halo bubbles and deflections of UHECRs

In this contribution, based on Ref. [1], we motivate a magnetic-field model in the Galactic-halo-bubbles region. Observations from Fermi-LAT [2–4] and eROSITA [5] show evidence of extended bubble-like structures in the Galactic-halo region, while WMAP [6], Planck [7], and S-PASS [8] also observed emission from extended Galactic structures at high Galactic latitudes. These non-thermal and thermal observations collectively motivate our investigation into the magnetic fields present in these Galactic halo bubbles. To constrain the parameters of our model, we combine it with an expression for the non-thermal electron distribution and generate sky maps of polarised synchrotron emission. These sky maps are then tested against Planck data at 30 GHz, showing the need for extended magnetic-field bubbles in the 2-10 μG range. Furthermore, we investigate the effect of these magnetic fields in the Galactic halo bubbles on the arrival directions of ultrahigh-energy cosmic rays (UHECRs). We conclude that present uncertainties in the field strengths can have significant consequences on the arrival directions of the cosmic rays and thereby on the source localisation.