Cosmic Ray Streaming Instability in the Interstellar Medium

Cole Holcomb, Princeton University

Cosmic rays (CRs) are charged particles moving relativistically through the galaxy with kinetic energies up to about 1020 eV. Despite having number densities nine orders of magnitude smaller than the background plasma through which they travel, CRs significantly contribute to the total energy density of the interstellar medium (ISM) due to their astronomically large kinetic energies. This contribution of energy to the ISM allows CRs to have important effects on the characteristics of galaxies, including setting the galactic pressure structure, regulating star formation and driving galactic-scale winds. We study the coupling of CRs to the galactic magnetic field and therefore also to the background ISM plasma by performing kinetic particle-in-cell (PIC) simulations. We use these results to discuss often-predicted, yet previously undemonstrated, effects CR interactions can have on the ISM.

Abstract Author(s): C. Holcomb, A. Spitkovsky, D. Caprioli