Cosmic ray composition at the ankle in the energy spectrum

Abstract

Recent results from the Pierre Auger Observatory and the Hi-Res array have been analysed hoping to derive a strong statement about the mass composition in the region of the ankle, where the change from Galactic to ExtraGalactic cosmic ray flux should take place, at least according to some theoretical predictions. It is shown that there are problems in reconciling the data with expectation. © Author(s) 2011.