Propagation of ultra-high energy protons in regular extragalactic magnetic fields

We study the proton flux expected from a local source or sources of ultra high energy cosmic rays (UHECR) in the presence of regular extragalactic magnetic fields. It is assumed that the source(s) of ultra-high energy protons, the observer and the magnetic field are all in a wall of matter concentration with dimensions characteristic of the supergalactic plane. For such configurations, the observed proton flux and the local cosmic ray energy spectrum depend strongly on the strength of the field and the orientation of the field relative to the observer's line of sight. We discuss the possibility that such effects could contribute to the excess of UHECR above $5.10^{19}$ eV, and that the sources of such particles may be missed if such magnetic fields are not taken into account