Cosmic-ray propagation in molecular clouds
arXiv:1305.5393 · doi:10.1007/978-3-642-35410-6_6
Abstract
Cosmic-rays constitute the main ionising and heating agent in dense, starless, molecular cloud cores. We reexamine the physical quantities necessary to determine the cosmic-ray ionisation rate (especially the cosmic ray spectrum at E < 1 GeV and the ionisation cross sections), and calculate the ionisation rate as a function of the column density of molecular hydrogen. Available data support the existence of a low-energy component (below about 100 MeV) of cosmic-ray electrons or protons responsible for the ionisation of diffuse and dense clouds. We also compute the attenuation of the cosmic-ray flux rate in a cloud core taking into account magnetic focusing and magnetic mirroring, following the propagation of cosmic rays along flux tubes enclosing different amount of mass and mass-to-flux ratios. We find that mirroring always dominates over focusing, implying a reduction of the cosmic-ray ionisation rate by a factor of 3-4 depending on the position inside the core and the magnetisation of the core.
To appear in "Cosmic Rays in Star-Forming Environments", Proceedings of the 2nd Session of the Sant Cugat Forum on Astrophysics. D. F. Torres and O. Reimer (Editors), 2013, Springer, 25 pages, 11 figures
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- Cosmic ray induced ionisation of a molecular cloud shocked by the W28 supernova remnant
- Helical Magnetic Fields in Molecular Clouds? A New Method to Determine the Line-of-Sight Magnetic Field Structure in Molecular Clouds
- Production of atomic hydrogen by cosmic rays in dark clouds
- Cosmic-ray propagation in molecular clouds
- Predicting HCN, HCO+, multi-transition CO, and dust emission of star-forming galaxies From local spiral and ultraluminous infrared galaxies to high-z star-forming and submillimeter galaxies
- Can a cosmic ray carrot explain the ionization level in diffuse molecular clouds?
- Temperature spectra of interstellar dust grains heated by cosmic-rays II: dark cloud cores
- Chemical exploration of Galactic cold cores