http://arxiv.org/abs/1312.7459
We use a kinetic-equation approach to propagation of ultra high energy cosmic ray protons and nuclei to infer possible implications of the data on spectrum and chemical composition collected by the Pierre Auger Observatory. Using a homogeneous source distribution, we show that a simultaneous fit to the spectrum, elongation rate $X_{max}(E)$ and dispersion $\sigma(X_{max})$ implies the injection of nuclei with very hard spectra. This leads however to underestimate the flux at energies $E\leq 5\times 10^{18}$ eV, thereby implying that an additional cosmic ray component is required, which needs to be of extragalactic origin. We discuss the nature of this additional component in terms of the recent findings of KASCADE-Grande on fluxes and chemical composition, which allows to describe the transition from Galactic to extragalactic cosmic rays.
Tue, 31 Dec 13
49/49
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