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ISRN Astronomy and Astrophysics
Volume 2011 (2011), Article ID 905015, 10 pages
Research Article

On the Cosmic Ray-Induced Ionization Rate in Molecular Clouds

V. A. Ambartsumian Byurakan Astrophysical Observatory, Byurakan 0213, Armenia

Received 30 January 2011; Accepted 13 March 2011

Academic Editors: C. Meegan and T. Wilson

Copyright © 2011 Ararat G. Yeghikyan. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The transformation of the energy dependence of the cosmic ray proton flux in the keV to GeV region is investigated theoretically when penetrating inside molecular clouds ( A v > 5 mag). The computations suggest that energy losses of the cosmic ray particles by interaction with the matter of the molecular cloud are principally caused by the inelastic (electronic) interaction potential; the transformed energy distribution of energetic protons is determined mainly by the column density of the absorbing medium. A cutoff of the cosmic ray spectrum inside clouds by their magnetic fields is also phenomenologically taken into account. This procedure allows a determination of environment-dependent ionization rates of molecular clouds. The theoretically predicted ionization rates are in good agreement with those derived from astronomical observations of H 3 + absorption lines in the spectrum of the cloud connected with the Herbig Be star LkH 𝛼 101.