Speaker
Description
The sharp change in slope of the ultrahigh-energy cosmic ray (UHECR) spectrum around 10^9.6 GeV (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. Recently, we introduced a very general model, in which for a range of source conditions, photo-disintegration of ultrahigh-energy nuclei in the region surrounding the UHECR accelerator naturally accounts for the observed spectrum and composition of the entire extragalactic component, which dominates above about 10^8.5 GeV. In this talk I will review the generalities of the model and show that starburst galaxies provide a compelling source example.
