Institute for Advanced Study/Princeton University Joint Astrophysics Colloquium

Cosmic rays comprise only about one billionth of interstellar particles in the Milky Way, but have as much energy as the thermal gas. Low energy cosmic rays affect the chemistry and thermodynamics of interstellar through collisional processes. Higher energy cosmic rays affect interstellar gas dynamics collisionlessly, though coupling to plasma waves. I will discuss the interactions between the cosmic rays and gas in the collisionless regime and discuss applications to galactic outflows, cosmic ray transport in galaxy clusters, and the propagation of cosmic rays through the intergalactic medium.