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Title: Ultra high energy cosmic rays: implications of Auger data for source spectra and chemical composition

Abstract

We use a kinetic-equation approach to describe the propagation of ultra high energy cosmic ray protons and nuclei and calculate the expected spectra and mass composition at the Earth for different assumptions on the source injection spectra and chemical abundances. When compared with the spectrum, the elongation rate X{sub max}(E) and dispersion σ(X{sub max}) as observed with the Pierre Auger Observatory, several important consequences can be drawn: a) the injection spectra of nuclei must be very hard, ∼ E{sup -γ} with γ∼ 1- 1.6; b) the maximum energy of nuclei of charge Z in the sources must be ∼ 5Z× 10{sup 18} eV, thereby not requiring acceleration to extremely high energies; c) the fit to the Auger spectrum can be obtained only at the price of adding an ad hoc light extragalactic component with a steep injection spectrum ∼ E{sup -2.7}). In this sense, at the ankle E{sub A}≈ 5× 10{sup 18} eV) all the components are of extragalactic origin, thereby suggesting that the transition from Galactic to extragalactic cosmic rays occurs below the ankle. Interestingly, the additional light extragalactic component postulated above compares well, in terms of spectrum and normalization, with the one recently measured by KASCADE-Grande.

Authors:
;  [1]
  1. INAF/Osservatorio Astrofisico di Arcetri, Largo E. Fermi, 5—50125 Firenze (Italy)
Publication Date:
OSTI Identifier:
22375834
Resource Type:
Journal Article
Journal Name:
Journal of Cosmology and Astroparticle Physics
Additional Journal Information:
Journal Volume: 2014; Journal Issue: 10; Other Information: Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1475-7516
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCELERATION; AUGER ELECTRON SPECTROSCOPY; CHEMICAL COMPOSITION; COSMIC RADIATION; ELONGATION; KINETIC EQUATIONS; NUCLEI; ORIGIN; PROTONS; SPECTRA

Citation Formats

Aloisio, R., Blasi, P., and Berezinsky, V., E-mail: aloisio@arcetri.astro.it, E-mail: berezinsky@lngs.infn.it, E-mail: blasi@arcetri.astro.it. Ultra high energy cosmic rays: implications of Auger data for source spectra and chemical composition. United States: N. p., 2014. Web. doi:10.1088/1475-7516/2014/10/020.
Aloisio, R., Blasi, P., & Berezinsky, V., E-mail: aloisio@arcetri.astro.it, E-mail: berezinsky@lngs.infn.it, E-mail: blasi@arcetri.astro.it. Ultra high energy cosmic rays: implications of Auger data for source spectra and chemical composition. United States. https://doi.org/10.1088/1475-7516/2014/10/020
Aloisio, R., Blasi, P., and Berezinsky, V., E-mail: aloisio@arcetri.astro.it, E-mail: berezinsky@lngs.infn.it, E-mail: blasi@arcetri.astro.it. Wed . "Ultra high energy cosmic rays: implications of Auger data for source spectra and chemical composition". United States. https://doi.org/10.1088/1475-7516/2014/10/020.
@article{osti_22375834,
title = {Ultra high energy cosmic rays: implications of Auger data for source spectra and chemical composition},
author = {Aloisio, R. and Blasi, P. and Berezinsky, V., E-mail: aloisio@arcetri.astro.it, E-mail: berezinsky@lngs.infn.it, E-mail: blasi@arcetri.astro.it},
abstractNote = {We use a kinetic-equation approach to describe the propagation of ultra high energy cosmic ray protons and nuclei and calculate the expected spectra and mass composition at the Earth for different assumptions on the source injection spectra and chemical abundances. When compared with the spectrum, the elongation rate X{sub max}(E) and dispersion σ(X{sub max}) as observed with the Pierre Auger Observatory, several important consequences can be drawn: a) the injection spectra of nuclei must be very hard, ∼ E{sup -γ} with γ∼ 1- 1.6; b) the maximum energy of nuclei of charge Z in the sources must be ∼ 5Z× 10{sup 18} eV, thereby not requiring acceleration to extremely high energies; c) the fit to the Auger spectrum can be obtained only at the price of adding an ad hoc light extragalactic component with a steep injection spectrum ∼ E{sup -2.7}). In this sense, at the ankle E{sub A}≈ 5× 10{sup 18} eV) all the components are of extragalactic origin, thereby suggesting that the transition from Galactic to extragalactic cosmic rays occurs below the ankle. Interestingly, the additional light extragalactic component postulated above compares well, in terms of spectrum and normalization, with the one recently measured by KASCADE-Grande.},
doi = {10.1088/1475-7516/2014/10/020},
url = {https://www.osti.gov/biblio/22375834}, journal = {Journal of Cosmology and Astroparticle Physics},
issn = {1475-7516},
number = 10,
volume = 2014,
place = {United States},
year = {2014},
month = {10}
}