On the transition from galactic to extragalactic cosmic-rays: Spectral and composition features from two opposite scenarios
By D. Allard, É. Parizot, Angela V. Olinto. 2005
140 citations recorded by the source corpus.
Abstract We study the phenomenology of cosmic-rays (CRs) at the galactic/extragalactic transition, focusing on two opposite models for the composition of the extragalactic (EG) component. Model A assumes a mixed source composition, with nuclear abundances similar to that of the low-energy CRs, while model B assumes that EG sources accelerate only protons. We study the limits within which both scenarios can reproduce the observed high-energy CR spectrum and composition. The ankle in model A is interpreted as the GCR/EGCR transition, while in model B it is the pair-production dip. Model A has a source spectrum ∝E−x with x ∼ 2.2–2.3, while model B requires x ∼ 2.6–2.7. We compare the predictions of both models with the available data on the energy evolution of the high-energy CR composition using the two main composition-related observables: Xmax and 〈lnA〉. We conclude that model A is currently favoured. Uncertainties are discussed and distinctive features of the two models are identified, which should allow one to distinguish between the models in the near future when more precise measurements are available with higher statistics experiments.
Subfields: Nuclear and High Energy Physics
View Paper: https://www.semanticscholar.org/paper/05b6ea0de7cf53cec00e9a04bbcdc92c69548b23
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In Nuclear and High Energy Physics
Citations in the corpus
- Study of Ultra-High Energy Cosmic Ray composition using Telescope Array’s Middle Drum detector and surface array in hybrid mode (2014, background): “nearby (. 100 Mpc). The nature of the composition of these cosmic rays is critical in determining whether this is in fact the mechanism, since such a cuto could be mimicked in a variety of other ways [6],[7],[8]. The composition of UHECR also has a major impact on predictions of the minimal extragal”
- The Astrophysics of Ultrahigh-Energy Cosmic Rays (2011, methodology): “The dip model can fit the observed spectrum if the injection is proton dominated (Berezinsky et al. 2005; Allard et al. 2007) or with at most a primordial proton to helium mix (Hillas 2006), which gives a clear path for distinguishing it from mixed composition models.”
- Cosmogenic neutrinos: parameter space and detectabilty from PeV to ZeV (2010, background): “Again in this scenario, heavy elements cannot exceed 10-15% of the total composition in order to fit the shape of the spectrum (Berezinsky et al., 2006; Allard et al., 2007).”