Are 10 EeV cosmic rays extragalactic? Theory of cosmic ray diffusion at high energy

Abstract

Auger Collaboration has reported a large-scale anisotropy in the arrival directions of cosmic rays above 8 EeV. The dipole direction, at 125${}^{\circ }$ from the Galactic center, is taken as an indication of an extragalactic origin of these cosmic rays. We show, both theoretically and by direct numerical simulations, that this is not necessarily true. Intermediate mass nuclei originating in the Galaxy and diffusing in the Galactic magnetic field can have a dipole anisotropy pointing away from the Galactic center. Our theory predicts a quadrupole anisotropy of the same order of magnitude as the dipole.

6 pages

References in corpus (1)

• Faraday rotation maps of disk galaxies

Cited by in corpus (2)

• Breaks in interstellar spectra of positrons and electrons derived from time-dependent AMS data
• Observable spectral and angular distributions of $\gamma$-rays from extragalactic ultrahigh energy cosmic ray accelerators: the case of extreme TeV blazars