The Effect of Our Cosmic Neighborhood’s Magnetic Field on UHECR Propagation

Although individual small-scale magnetized structures in our Galaxy do not have a significant impact on the propagation of UHECRs of energy greater than 1 EeV, they have the potential to influence our reconstruction of the large-scale magnetic field commonly derived from synchrotron and Faraday rotation data. In this context, the Local Bubble - a cavity of hot gas surrounded by a thick magnetized shell extending roughly 100 pc around the Sun - is a very important element to take into account. Here, we focus on the effects of including the Local Bubble and its magnetized shell to reconstruct the large-scale Galactic magnetic field and further explore possible consequences for propagation studies of UHECRs. We find that the magnetized shell of the Local Bubble implies a foreground for Galactic magnetic field observables that leads to changes in the characterization of the magnetic field at large scales, leading to changes in backtracking predictions. These changes are of the order of other uncertainties of global Galactic magnetic field models, and therefore a better understanding of the Local Bubble is needed to improve the precision of backtracking of UHECRs through the Galaxy.