  The origin of the most energetic cosmic ray particles is one of the most
important open problems in astrophysics. Despite a big experimental effort done
in the past years, the sources of these very energetic particles remain
unidentified. Therefore, their distribution on the Universe and even their
space density are still unknown. It has been shown that different spatial
configurations of the sources lead to different energy spectra and composition
profiles (in the case of sources injecting heavy nuclei) at Earth. These
ensemble fluctuations are more important at the highest energies because only
nearby sources, which are necessarily few, can contribute to the flux observed
at Earth. This is due to the interaction of the cosmic rays with the low energy
photons of the radiation field, present in the intergalactic medium, during
propagation. It is believed that the intergalactic medium is permeated by a
turbulent magnetic field. Although at present it is still unknown, there are
several constraints for its intensity and coherence length obtained from
different observational techniques. Charged cosmic rays are affected by the
intergalactic magnetic field because of the bending of their trajectories
during propagation through the intergalactic medium. In this work, the
influence of the intergalactic magnetic field on the ensemble fluctuations is
studied. Sources injecting only protons and only iron nuclei are considered.
The ensemble fluctuations are studied for different values of the density of
sources compatible with the constraints recently obtained from cosmic ray data.
Also, the possible detection of the ensemble fluctuations in the context of the
future JEM-EUSO mission is discussed.
