The Large Scale Impact of Localized Cosmic Ray Injection

Supernova explosions are a major driver of galaxy evolution, and cosmic rays are a major component of that driving. This 'cosmic ray feedback' presents a challenging multiscale problem in galaxy simulations. The supernova explosions on small scales (<< 1pc) which accelerate cosmic rays eventually produce the background of cosmic rays streaming throughout a galactic disk. They also affect the vertical structure of a galactic disk on large scales (> 1kpc). We examine the connection of cosmic ray production by supernovae to the vertical structure of a galactic disk using galactic patch simulations in the Athena++ code. We randomly place point-like injections of cosmic rays in the mid-plane of a 1kpc² patch of a galactic disk. These injections disrupt the vertical hydrostatic equilibrium on large scales. We observe significantly different results when using random, point-like injections instead of a constant cosmic ray flux.