Anisotropic diffusion and the cosmic ray anisotropy

Abstract

We argue that the diffusion of cosmic rays in the Galactic magnetic field has to be strongly anisotropic. As a result, the number of CR sources contributing to the local CR flux is strongly reduced. The CR density is therefore less smooth, and the contribution of individual sources to the CR dipole anisotropy becomes more prominent. In the case of anisotropic diffusion, the observed plateau in the CR dipole anisotropy around 2–20 TeV can be explained by a 2–3 Myr old CR source which dominates the local CR flux in this energy range.