Heating of molecular-hydrogen clouds by cosmic rays and x-rays

view Abstract Citations (85) References (81) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Heating of Molecular-Hydrogen Clouds by Cosmic Rays and X-Rays Glassgold, A. E. ; Langer, William D. Abstract We calculate the heating of molecular clouds, whose main constituent is H2, by low-energy cosmic rays and soft X-rays. The heating of molecular hydrogen is qualitatively different from the atomic-hydrogen case because of vibrational and rotational excitation modes and dissociation. We discuss these properties and determine how the heat is deposited by the primary ionization and by secondary and higher-generation electrons. We find that at zero electron concentration a 2-MeV proton produces 15 eV of heating after an ionization of H2 in which it loses 33 eV. For a fractional electron concentration of 10-2, which probably is an upper limit for molecular clouds, this heating is 17 eV. For X-rays we find that 35 percent of the initial energy is effective in heating the gas. Above 100 eV, each absorbed X-ray produces approximately 25(E /keV) electrons. The additional effects arising from the presence of helium are included, and lead to an increase in the heating and the primary ionization rate by a factor of 3 for X-rays. Subject headings: cosmic rays - molecules, interstellar - nebulae - X-rays Publication: The Astrophysical Journal Pub Date: December 1973 DOI: 10.1086/152552 Bibcode: 1973ApJ...186..859G full text sources ADS |