Powered by Indico
v3.2
Galactic cosmic rays (CRs) are a ubiquitous source of ionisation of the interstellar gas, competing with UV and X-ray photons as well as natural radioactivity in determining the fractional abundance of electrons, ions and charged dust grains in molecular clouds and circumstellar discs, and thus controlling a great deal of the dynamical and chemical processes occurring in these objects. The transport regime of the penetration of galactic CRs and their further propagation depend on a variety of conditions. Understanding these conditions is essential in determining whether the CRs can stream freely along the magnetic field lines, or they experience significant scattering on the field fluctuations, leading to the diffusive propagation. I will summarize the recent progress in the theory of CR transport in clouds and disks, and discuss the resulting effect on the gas ionization and heating for a broad range of densities, from low-density envelopes of molecular clouds to densest regions of circumstellar disks.