Lensing effects of ultra-high-energy cosmic rays propagating in the Galactic magnetic field

Abstract: Since ultra-high-energy cosmic rays (UHECRs) are electrically charged particles, they are deflected by magnetic fields. Those magnetic fields can act as lenses, altering their trajectories and (de)magnifying their apparent source images. These deflections of UHECR trajectories can lead to phenomena such as the appearance of multiple images of an extragalactic source. In this study, we investigate the influence of the Galactic Magnetic Field (GMF) on the propagation of UHECRs, considering four different realistic models for the GMF: the PT11, the JF12, the UF23, and the KST24 models. We investigate how an isotropic flux on Earth would have entered the edge of the Galaxy for different rigidity values from 1 to 100 EV. In addition, we investigate the appearance of multiple images of astrophysical point sources. Furthermore, we analyze the modification of the cosmic ray flux from a source as a function of the rigidity and its dependence on the chosen GMF model. Since the deflection induced by the magnetic field depends on the rigidity of the particle, the effects vary among different nuclear species. Consequently, our findings can have implications for interpreting mass-composition and anisotropy observations, as the rigidity-dependent deflections directly alter the observed UHECR arrival direction distribution.