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Cosmic Ray Anisotropy as Signature for the Transition from Galactic to Extragalactic Cosmic Rays
Giacinti G., Kachelriess M., Semikoz D.V., Sigl G.
Journal of Cosmology and Astroparticle Physics 07 (2012) 031 - http://hal.archives-ouvertes.fr/hal-00713437
Physique/Astrophysique/Phénomènes cosmiques de haute energie
Planète et Univers/Astrophysique/Phénomènes cosmiques de haute energie
Cosmic Ray Anisotropy as Signature for the Transition from Galactic to Extragalactic Cosmic Rays
G. Giacinti1, 2, 3, M. Kachelriess2, D.V. Semikoz1, G. Sigl3
1 :  APC - UMR 7164 - AstroParticule et Cosmologie
CNRS : UMR7164 – IN2P3 – Observatoire de Paris – Université Paris VII - Paris Diderot – CEA : DSM/IRFU
APC - UMR 7164, Université Paris Diderot, 10 rue Alice Domon et Léonie Duquet, case postale 7020, F-75205 Paris Cedex 13
2 :  NTNU - Institutt for fysikk, NTNU
Institutt for fysikk, NTNU, Trondheim
3 :  ITP - Institut für Theoretische Physik
Universität Hamburg
Luruper Chaussee 149, D-22761
We constrain the energy at which the transition from Galactic to extragalactic cosmic rays occurs by computing the anisotropy at Earth of cosmic rays emitted by Galactic sources. Since the diffusion approximation starts to loose its validity for E/Z >~ 10^(16-17) eV, we propagate individual cosmic rays using Galactic magnetic field models and taking into account both their regular and turbulent components. The turbulent field is generated on a nested grid which allows spatial resolution down to fractions of a parsec. If the primary composition is mostly light or intermediate around E ~ 10^18 eV, the transition at the ankle is ruled out, except in the unlikely case of an extreme Galactic magnetic field with strength >~ 10 {\mu}G. Therefore, the fast rising proton contribution suggested by KASCADE-Grande data between 10^17 eV and 10^18 eV should be of extragalactic origin. In case heavy nuclei dominate the flux at E >~ 10^18 eV, the transition energy can be close to the ankle, if Galactic cosmic rays are produced by sufficiently frequent transients as e.g. magnetars.

Journal of Cosmology and Astroparticle Physics
Publisher Institute of Physics (IOP)
ISSN 1475-7508 (eISSN : 1475-7516)
Articles dans des revues avec comité de lecture

18 pages, 7 figures

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