The sharp change in slope of the ultra-high energy cosmic ray (UHECR) spectrum around 10^{ 18.6} eV (the ankle), combined with evidence of a light but extragalactic component near and below the ankle which evolves to intermediate composition above, has proved exceedingly challenging to understand theoretically. We show that for a range of source conditions, photo-disintegration of ultra-high energy nuclei in the region surrounding a UHECR accelerator naturally accounts for the observed spectrum and composition of the entire extragalactic component, which dominates above about 10^{ 17.5} eV. The mechanism has a clear signature in the spectrum and flavors of neutrinos.
Categories: astro-ph.HE