Abstract
We show that the complex shape of the cosmic ray (CR) spectrum, as recently measured by PAMELA and inferred from Fermi-LAT -ray observations of molecular clouds in the Gould belt, can be naturally understood in terms of basic plasma astrophysics phenomena. A break from a harder to a softer spectrum at rigidity follows from a transition from transport dominated by advection of particles with Alfvén waves to a regime where diffusion in the turbulence generated by the same CRs is dominant. A second break at happens when the diffusive propagation is no longer determined by the self-generated turbulence, but rather by the cascading of externally generated turbulence (for instance due to supernova bubbles) from large spatial scales to smaller scales where CRs can resonate. Implications of this scenario for the cosmic ray spectrum, grammage, and anisotropy are discussed.
- Received 30 May 2012
DOI:https://doi.org/10.1103/PhysRevLett.109.061101
© 2012 American Physical Society
Synopsis
Cosmic Drift
Published 9 August 2012
Changes in the diffusion constant of cosmic rays due to self-induced turbulence may explain unexpected features in the cosmic-ray spectrum.
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