Abstract
Energetic gamma rays (GeV to TeV photon energy) have been detected toward several supernova remnants (SNR) that are associated with molecular clouds. If the gamma rays are produced mainly by hadronic processes rather than leptonic processes like bremsstrahlung, then the flux of energetic cosmic ray nuclei (>1GeV) required to produce the gamma rays can be inferred at the site where the particles are accelerated in SNR shocks. It is of great interest to understand the acceleration of the cosmic rays of lower energy (<1GeV) that accompany the energetic component. These particles of lower energy are most effective in ionizing interstellar gas, which leaves an observable imprint on the interstellar ion chemistry. A correlation of energetic gamma radiation with enhanced interstellar ionization can thus be used to support the hadronic origin of the gamma rays and to constrain the acceleration of ionizing cosmic rays in SNR. Using observational gamma ray data, the primary cosmic ray proton spectrum can be modeled for E>1GeV, and careful extrapolation of the spectrum to lower energies offers a method to calculate the ionization rate of the molecular cloud.
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Acknowledgements
We would like to thank R. Schlickeiser and P.L. Biermann for helpful and inspiring discussions. We also want to thank Marco Padovani for very helpful comments. JKB, SC and FS acknowledge funding from the DFG, Forschergruppe “Instabilities, Turbulence and Transport in Cosmic Magnetic Fields” (FOR1048, Project BE 3714/5-1) and from the Junges Kolleg (Nordrheinwestfälische Akademie der Wissenschaften und der Künste). JHB is grateful to the Swedish National Space Board for support. We further acknowledge the support by the Research Department of Plasmas with Complex Interactions (Bochum).
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Schuppan, F., Becker, J.K., Black, J.H., Casanova, S., Mandelartz, M. (2013). Cosmic-Ray-Induced Ionization in Molecular Clouds Adjacent to Supernova Remnants. In: Torres, D., Reimer, O. (eds) Cosmic Rays in Star-Forming Environments. Astrophysics and Space Science Proceedings, vol 34. Springer, Berlin, Heidelberg. https://doi.org/10.1007/978-3-642-35410-6_24
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DOI: https://doi.org/10.1007/978-3-642-35410-6_24
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