A signature of EeV protons of Galactic origin

Understand

We investigate signatures that would be produced in the spectrum and sky distribution of UHECR by a population of the Galactic sources of high-energy protons in the energy range around 1~EeV, i.e., around the diffusive-to-ballistic transition.

• In this regime, the CR flux has to be calculated numerically.
• We employ the approach that consists in backtracking anti-protons from Earth through the Galaxy and integrating the source emissivity along the trajectory.
• This approach makes evident two generic features of the transition region: sharp increase of the total flux as the energy decreases across the transition region, and its strong anisotropy (appearance of a bright compact spot) all the way until the onset of the diffusive regime.