  It is argued that if cosmic rays penetrate into molecular clouds, the total
energy they lose can exceed the energy from galactic supernovae shocks. It is
shown that most likely galactic cosmic rays interacting with the surface layers
of molecular clouds are efficiently reflected and do not penetrate into the
cloud interior. Low-energy cosmic rays ($E<1$ GeV) that provide the primary
ionization of the molecular cloud gas can be generated inside such clouds by
multiple shocks arising due to supersonic turbulence.
