Cosmic-ray ionisation of molecular clouds

Séminaire IPAG de Marco Padovani (CSIC-IEEC, Barcelona), jeudi 3 novembre 2011 à 11h00, IPAG seminar room

Cosmic-rays constitute the main ionising and heating agent in dense, starless, molecular cloud cores. The main goal of this work is the calculation of the ionisation rate in a cloud resulting from the collisions between cosmic-ray particles (protons and electrons) and the matter constituting the cloud, mainly molecular hydrogen. We reexamine the physical quantities necessary to determine the cosmic-ray ionisation rate (especially the cosmic ray spectrum at E < GeV and the ionisation cross sections), and calculate the ionisation rate as a function of the column density of molecular hydrogen, through careful numerical integrations. Finally, we compute the attenuation of the cosmic-ray flux rate in a cloud core taking into account magnetic focusing, magnetic mirroring, and all relevant energy loss processes.