Type: Article
Publication Date: 2005-04-11
Citations: 103
DOI: https://doi.org/10.1103/physrevd.71.083007
Recent work suggests that the cosmic-ray spectrum may be dominated by Galactic sources up to $\ensuremath{\sim}{10}^{17.5}$ eV, and by an extra-Galactic component beyond, provided this latter cuts off below the transition energy. Here it is shown that this cut-off could be interpreted in this framework as a signature of extra-galactic magnetic fields with equivalent average strength $B$ and coherence length ${l}_{\mathrm{c}}$ such that $B\sqrt{{l}_{\mathrm{c}}}\ensuremath{\sim}2\ensuremath{-}3\ifmmode\cdot\else\textperiodcentered\fi{}{10}^{\ensuremath{-}10}\text{ }\text{ }\mathrm{G}\ifmmode\cdot\else\textperiodcentered\fi{}{\mathrm{Mpc}}^{1/2}$, assuming ${l}_{\mathrm{c}}<{r}_{\mathrm{L}}$ (Larmor radius at $\ensuremath{\lesssim}{10}^{17}$ eV) and continuously emitting sources with density ${10}^{\ensuremath{-}5}{\text{ }\text{ }\mathrm{Mpc}}^{\ensuremath{-}3}$. The extra-Galactic flux is suppressed below $\ensuremath{\sim}{10}^{17}$ eV as the diffusive propagation time from the source to the detector becomes larger than the age of the Universe.