  The description of the transport of cosmic rays in magnetized media is
central to both acceleration and propagation of these particles in our Galaxy
and outside. The investigation of the process of particle acceleration,
especially at shock waves, has already emphasized that non-linear effects such
as self-generation of waves and dynamical reaction of cosmic rays on the
background plasmas, are crucial if to achieve a physical understanding of the
origin of cosmic rays. Here we discuss how similar non-linear effects on
Galactic scales may affect the propagation of cosmic rays, not only through the
excitation of plasma waves important for particle scattering, but also by
inducing the motion of the interstellar medium in the direction opposite to the
gravitational pull exerted by matter in the Galaxy, thereby resulting in the
launching of a wind. The recent discovery of several unexpected features in
cosmic ray spectra (discrepant hardening, spectral breaks in the H and He
spectra, rising positron fraction and unexpectedly hard antiproton spectrum)
raises the question of whether at least some of these effects may be attributed
to poorly understood aspects of cosmic ray transport.
