Don Ellison
      
North Carolina State University, Raleigh, NC, USA

Cosmic ray production in young supernova remnant (SNR) shocks is expected to be efficient and strongly nonlinear. In nonlinear, first-order Fermi acceleration, compression ratios will be higher and the shocked temperature lower than test-particle, Rankine-Hugoniot relations predict (in extreme cases, the shocked gas can be simultaneously 10 times cooler and 10 times denser than test-particle predictions). Thus, efficient particle acceleration connects cosmic ray production with the properties of the shock heated interstellar medium and influences the dynamics of the remnants and modifies the X-ray line and continuum emission. We describe the nonlinear effects using a simple, self-consistent model of shock acceleration and calculate broad-band continuum emission from selected young SNRs.