The origin of cosmic rays (CRs) has puzzled scientists since
the pioneering discovery by Victor Hess in 1912. In the last decade, however,
modern supercomputers have opened a new window on the processes regulating
astrophysical collisionless plasmas, allowing the
study of CR acceleration via first-principles kinetic simulations; at the same
time, new generations of X-ray and gamma-ray telescopes have been collecting
evidence that Galactic CRs are accelerated in the blast waves of supernova
remnants (SNRs).
I present state-of-the-art particle-in-cells simulations of
non-relativistic shocks, in which ion and electron acceleration efficiency, and
magnetic field amplification, are studied in detail as a function of the shock
parameters. I then discuss the theoretical and observational counterparts of
these findings, comparing them with predictions of diffusive shock acceleration
theory, and with multi-wavelength observations of young SNRs.