Comparison of UHECR spectra from necklaces and vortons
  Cosmic rays of energy higher than 10^19 eV may be explained by topological defects produced in the early stages of universe. Two suitable alternatives are: necklaces formed by magnetic monopoles connected by strings, and vortons which are loops stabilized by superconducting currents. The former are uniformly distributed in the universe, may account for cosmic rays above the ankle, suffer a transient GZK cutoff with a subsequent recovery and isotropy of observations is expected. The latter are concentrated in the galactic halo, require an additional extragalactic contribution between the ankle and the GZK cutoff, beyond which give a harder component and predict anisotropy related to mass concentration. 
Luis Masperi and Milva Orsaria