Carl Blaksley, Etienne Parizot
We study a generic class of models for ultra-high energy cosmic ray (UHECR)
phenomenology, in which the sources accelerate protons and nuclei with a
power-law spectrum having the same index, but with different values for the
maximum proton energies, distributed according to a power-law. We show that,
for energies sufficiently lower than the maximum proton energy, such models are
equivalent to single-type source models, with a larger effective power law
index and a heavier composition at the source. We calculate the resulting
enhancement of the abundance of nuclei, and find typical values of a factor
2-10 for Fe nuclei. At the highest energies, the heavy nuclei enhancement
ratios become larger, and the granularity of the sources must also be taken
into account. We conclude that the effect of a distribution of maximum energies
among sources must be considered in order to understand both the energy
spectrum and the composition of UHECRs, as measured on Earth.
View original:
http://arxiv.org/abs/1111.1607
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