1,996 research outputs found
Imprint of a 2 Myr old source on the cosmic ray anisotropy
We study numerically the anisotropy of the cosmic ray (CR) flux emitted by a
single source calculating the trajectories of individual CRs. We show that the
contribution of a single source to the observed anisotropy is instead
determined solely by the fraction the source contributes to the total CR
intensity, its age and its distance,and does not depend on the CR energy at
late times. Therefore the observation of a constant dipole anisotropy indicates
that a single source dominates the CR flux in the corresponding energy range. A
natural explanation for the plateau between 2--20 TeV observed in the CR
anisotropy is thus the presence of a single, nearby source. For the source age
of 2 Myr, as suggested by the explanation of the antiproton and positron data
from PAMELA and AMS-02 through a local source [arXiv:astro-ph/1504.06472], we
determine the source distance as pc. Combined with the contribution
of the global CR sea calculated in the escape model, we can explain
qualitatively the data for the dipole anisotropy. Our results suggest that the
assumption of a smooth CR source distribution should be abandoned between 200
GeV and 1 PeV.Comment: 4 pages, 4 eps figures; v2: minor changes, to appear in ApJ
- …