Anti-GZK effect in UHECR diffusive propagation

We discuss the antiGZK effect in the diffusive propagation of UHE protons, which consists in a jump-like increase of the maximum distance from which UHE protons can reach an observer. The position of this jump, $E_j \approx 2\times 10^{18}$ eV, is determined exclusively by energy losses (transition from adiabatic to pair-production energy losses) and it is independent of the diffusion parameters. The diffuse spectrum obtains a low-energy steepening approximately at this energy.