Cosmic Rays, Dust, and the Mixing of Supernova Ejecta into the Interstellar Medium in Superbubbles

Abstract

Most of the galactic core-collapse supernovae occur in OB associations that produce superbubbles, and thus, the bulk of the cosmic rays are accelerated in the cores of such superbubbles by the shock waves from these supernovae. Here we show that the initial mixing of the freshly synthesized elements from such supernovae with the gas and dust in the interstellar medium also occurs in the cores of these superbubbles, and that the unique composition of the galactic cosmic rays can be produced there by suprathermal ion injection from interactions of this mix of dust, gas, and supernova shocks. We further show that the basic features of the cosmic-ray composition provide a unique measure of the mixing ratio of the fresh supernova ejecta and the old interstellar medium in this initial phase of interstellar mixing.