In the last decades, the improvement of high energy instruments has enabled a
deeper understanding of the Cosmic Ray origin issue. In particular, the
gamma-ray satellites AGILE (Astrorivelatore Gamma ad Immagini LEggero) and
Fermi-LAT (Fermi-Large Area Telescope) have strongly contributed to the
confirmation of direct involvement of Supernova Remnants in Cosmic Ray
energization. Despite several attempts to fit experimental data assuming the
presence of freshly accelerated particles, the scientific community is now
aware that the role of pre-existing Cosmic Ray re-acceleration cannot be
neglected. In this work, we highlight the importance of pre-existing Cosmic Ray
re-acceleration in the Galaxy showing its fundamental contribution in middle
aged Supernova Remnant shocks and in the forward shock of stellar winds.Comment: 16 pages, 4 figure
