Evidence for the Nonlinear Transport of Galactic Cosmic Rays

Abstract

The measured decrease of the abundance ratio of secondary to primary Galactic cosmic-ray nuclei is explained by the increase of the cosmic-ray parallel mean free path with magnetic rigidity λ∥ ∝ R0.6 that results from the weakly nonlinear transport theory of cosmic rays in the turbulent Galactic magnetic fields. Because the ratio of fluctuating to ordered magnetic fields in the Galaxy qL = (δB/B0)2 is large, this nonlinear transport theory has to be favored over the traditional quasi-linear theory that requires very small values qL≪. 1. Our explanation provides an alternative to Galactic transport theories of cosmic rays with significant distributed stochastic acceleration. © 2005. The American Astronomical Society. All rights reserved.