Cosmic-ray evolution in Parker-unstable Galactic magnetic fields

We discuss the Parker instability of the Galactic interstellar medium, focusing on the cosmic-ray gas injection by supernova remnants and its propagation, through the diffusion equation. We describe the Parker instability in the thin flux-tube approximation and solve the flux-tube and the diffusion equations numerically. We find that the Parker instability triggered by the injection of cosmic rays in supernova remnants is faster than the Parker instability excited by the "small vertical perturbation" and that there is no lower limit for the horizontal scale of the raised magnetic loops. We find a very strong dynamo effect and discuss the vertical transport of cosmic rays in the Galactic disk across the large-scale horizontal magnetic field.