skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Cosmic ray anisotropy as signature for the transition from galactic to extragalactic cosmic rays

Abstract

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{sup 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. Assuming sufficiently frequent Galactic CR sources, the dipole amplitude computed for a mostly light or intermediate primary composition exceeds the dipole bounds measured by the Auger collaboration around E ≈ 10{sup 18} eV. Therefore, a transition at the ankle or above would require a heavy composition or a rather extreme Galactic magnetic field with strength ∼>10 μG. Moreover, the fast rising proton contribution suggested by KASCADE-Grande data between 10{sup 17} eV and 10{sup 18} eV should be of extragalactic origin. In case heavy nuclei dominate the flux at E∼>10{sup 18} eV, the transition energy can be close to the ankle, if Galactic CRs are produced by sufficiently frequent transients as e.g. magnetars.

Authors:
;  [1];  [2];  [3]
  1. Institutt for fysikk, NTNU, Trondheim (Norway)
  2. AstroParticle and Cosmology (APC), Paris (France)
  3. II. Institut für Theoretische Physik, Universität Hamburg, Hamburg (Germany)
Publication Date:
OSTI Identifier:
22280040
Resource Type:
Journal Article
Journal Name:
Journal of Cosmology and Astroparticle Physics
Additional Journal Information:
Journal Volume: 2012; Journal Issue: 07; 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; ANISOTROPY; APPROXIMATIONS; ASTROPHYSICS; COSMIC NUCLEI; COSMIC RADIATION; DIFFUSION; DIPOLES; EEV RANGE; HEAVY NUCLEI; MAGNETIC FIELDS; MAGNETIC STARS; MILKY WAY; PEV RANGE; PROTONS; SPATIAL RESOLUTION; TRANSIENTS

Citation Formats

Giacinti, G., Kachelrieß, M., Semikoz, D.V., and Sigl, G. Cosmic ray anisotropy as signature for the transition from galactic to extragalactic cosmic rays. United States: N. p., 2012. Web. doi:10.1088/1475-7516/2012/07/031.
Giacinti, G., Kachelrieß, M., Semikoz, D.V., & Sigl, G. Cosmic ray anisotropy as signature for the transition from galactic to extragalactic cosmic rays. United States. doi:10.1088/1475-7516/2012/07/031.
Giacinti, G., Kachelrieß, M., Semikoz, D.V., and Sigl, G. Sun . "Cosmic ray anisotropy as signature for the transition from galactic to extragalactic cosmic rays". United States. doi:10.1088/1475-7516/2012/07/031.
@article{osti_22280040,
title = {Cosmic ray anisotropy as signature for the transition from galactic to extragalactic cosmic rays},
author = {Giacinti, G. and Kachelrieß, M. and Semikoz, D.V. and Sigl, G.},
abstractNote = {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{sup 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. Assuming sufficiently frequent Galactic CR sources, the dipole amplitude computed for a mostly light or intermediate primary composition exceeds the dipole bounds measured by the Auger collaboration around E ≈ 10{sup 18} eV. Therefore, a transition at the ankle or above would require a heavy composition or a rather extreme Galactic magnetic field with strength ∼>10 μG. Moreover, the fast rising proton contribution suggested by KASCADE-Grande data between 10{sup 17} eV and 10{sup 18} eV should be of extragalactic origin. In case heavy nuclei dominate the flux at E∼>10{sup 18} eV, the transition energy can be close to the ankle, if Galactic CRs are produced by sufficiently frequent transients as e.g. magnetars.},
doi = {10.1088/1475-7516/2012/07/031},
journal = {Journal of Cosmology and Astroparticle Physics},
issn = {1475-7516},
number = 07,
volume = 2012,
place = {United States},
year = {2012},
month = {7}
}