Inferring Particle Acceleration in Supernova Remnant Shocks

Particle acceleration in Supernova Remnant shocks has been known since the discovery of synchrotron emission from young SNRs. However, it has been difficult to pin down the acceleration efficiency even for the electrons observed. This paper summarizes the observational constraints on electron acceleration, then discusses constraints on the ratio of cosmic ray to gas pressure based on compression and electron temperature, and finally discusses evidence for shock wave precursors and constraints on the cosmic ray diffusion coefficient.