The bulk of cosmic rays originate in the Milky Way, most likely in supernova explosions. I will discuss the physics aspects of the interaction between charged particles and the environment that are at the very basis of both particle acceleration and propagation throughout the Galaxy and beyond. While we learned a lot from recent cosmic ray and gamma ray observations, we are also being surprised by a bunch of new phenomena. I will discuss these recent developments and their implications for cosmic ray physics.

Host: Damiano Caprioli, Astrophysical Sciences, Princeton University