Decaying neutron propagation in the Galaxy and the Cosmic Ray anisotropy at 1 EeV

Abstract

We study the cosmic ray arrival distribution expected from a source of neutrons in the galactic center at energies around 1 EeV and compare it with the anisotropy detected by AGASA and SUGAR. Besides the point-like signal in the source direction produced by the direct neutrons, an extended signal due to the protons produced in neutron decays is expected. This associated proton signal also leads to an excess in the direction of the spiral arm. For realistic models of the regular and random galactic magnetic fields, the resulting anisotropy as a function of the energy is obtained. We find that for the anisotropy to become sufficiently suppressed below E\sim 10^{17.9}eV, a significant random magnetic field component is required, while on the other hand, this also tends to increase the angular spread of the associated proton signal and to reduce the excess in the spiral arm direction. The source luminosity required in order that the right ascension anisotropy be 4% for the AGASA angular exposure corresponds to a prediction for the point-like flux from direct neutrons compatible with the flux detected by SUGAR. We also analyse the distinguishing features predicted for a large statistics southern observatory.

arXiv comment14 pages, 6 figures, minor changes to match published version

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• Cosmic Rays: The Second Knee and Beyond
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• Sgr A East as a possible high energy neutron factory in the Galactic Centre
• Detectable neutrino fluxes due to enhanced cosmic ray densities in the Galactic Center region
• Search for Point-Like Sources of Cosmic Rays with Energies above 10^18.5 eV in the HiRes-I Monocular Data-Set
• Search for Sources of High Energy Neutrons with Four Years of Data from the IceTop Detector
• Experimental Ultra--High-Energy Cosmic Ray Physics
• Astronomy with ultra high-energy particles
• Propagation of Ultra-High Energy Cosmic Rays in Extragalactic Magnetic Fields
• Cosmic Rays at the Highest Energies -- First Data from the Pierre Auger Observatory --
• Anisotropy studies around the galactic center