Anti-GZK effect in UHECR diffusive propagation

We discuss the antiGZK effect in the diffusive propagation of UHE protons in intergalactic magnetic fields, 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 presents a low-energy steepening approximately at this energy, which is very close to the position of the second knee observed in the cosmic ray spectrum. The dip, seen in the universal spectrum as a signature of the interaction with the CMB radiation, is also present in the case of diffusive propagation in magnetic fields.