2015/03/31 by G. Morlino, S. Gabici · 1 citation
Physics and Astronomy · #astro-ph.HE
paper · pdf · doi:10.1093/mnrasl/slv074
published as Monthly Notices of the Royal Astronomical Society: Letters 2015 451 (1): L100-L104 · 5 pages, 4 figures. Published in MNRAS Letters. Minor changes to match the published version
arxiv created 2015/06/16 · arxiv updated 2015/06/17
Cosmic rays are a fundamental source of ionization for molecular and diffuse clouds, influencing their chemical, thermal, and dynamical evolution. The amount of cosmic rays inside a cloud also determines the γ-ray flux produced by hadronic collisions between cosmic rays and cloud material. We study the spectrum of cosmic rays inside and outside of a diffuse cloud, by solving the stationary transport equation for cosmic rays including diffusion, advection and energy losses due to ionization of neutral hydrogen atoms. We found that the cosmic ray spectrum inside a diffuse cloud differs from the one in the interstellar medium for energies smaller than Ebr≈ 100 MeV, irrespective of the model details. Below Ebr, the spectrum is harder (softer) than that in the interstellar medium if the latter is a power law ∝ p-s with s larger (smaller) than ∼ 0.42.