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ASTRA Proceedings An open-access journal for refereed proceedings in extraterrestrial research
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Articles | Volume 2
ASTRA Proc., 2, 51–55, 2015
ASTRA Proc., 2, 51–55, 2015

  08 Oct 2015

08 Oct 2015

A solution to the cosmic ray anisotropy problem

P. Mertsch1 and S. Funk2 P. Mertsch and S. Funk
  • 1Kavli Institute for Particle Astrophysics & Cosmology, 2575 Sand Hill Road, M/S 29, Menlo Park, CA 94025, USA
  • 2Erlangen Center for Astroparticle Physics (ECAP), Friedrich-Alexander Universität Erlangen-Nürnberg, Erlangen, Germany

Abstract. Observations of the cosmic ray (CR) anisotropy are widely advertised as a means of finding nearby sources. This idea has recently gained currency after the discovery of a rise in the positron fraction and is the goal of current experimental efforts, e.g., with AMS-02 on the International Space Station. Yet, even the anisotropy observed for hadronic CRs is not understood, in the sense that isotropic diffusion models overpredict the dipole anisotropy in the TeV–PeV range by almost two orders of magnitude. Here, we consider two additional effects normally not considered in isotropic diffusion models: anisotropic diffusion due to the presence of a background magnetic field and intermittency effects of the turbulent magnetic fields. We numerically explore these effect by tracking test-particles through individual realisations of the turbulent field. We conclude that a large misalignment between the CR gradient and the background field can explain the observed low level of anisotropy.

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