Astrophysics and Space Science

, Volume 68, Issue 1, pp 27–48 | Cite as

A diffusion model for cosmic ray propagation in the Galaxy

  • Jon M. Wallace


A diffusion model for the propagation of relativistic nuclear cosmic rays in the Galaxy is developed. The model has two nonstandard features: The escape of cosmic-ray particles from the Galaxy is simulated by a term in the diffusion equations, rather than the imposition of boundary conditions on the diffusion solution at the surface of the confinement region. And an age-dependent, locally-averaged effective gas distribution is employed in the diffusion equations. The model simulates free-particle outflow at the Galactic boundary. The model is fit to chemical composition data in the 0.3–5 GeV per nucleon range. It is then consistent with the large-scale Galactic γ-ray data, radio halo data, energy constraints on the assumed supernova sources, and, when extended to very high energies, cosmic-ray anisotrophy data. From the fit we conclude that the cosmic rays are confined in a large flattened or quasis-pherical halo with a scale height in the range 3–6 kpc and an average Galactic escape time of ∼108 yr.


Diffusion Model Diffusion Equation Scale Height Diffusion Solution Energy Constraint 
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Copyright information

© D. Reidel Publishing Co 1980

Authors and Affiliations

  • Jon M. Wallace
    • 1
  1. 1.Los Alamos Scientific LaboratoryLos AlamosU.S.A.

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