The investigator will consider four issues basic to improving the understanding of diffusive acceleration of particles at shocks: (1) 'injection' of low energy or thermal particles into the diffusive shock acceleration process, (2) generation and evolution of the strong turbulence responsible for scattering the energetic particles in the vicinity of a shock, (3) development of non-quasi-linear models of the cosmic ray/energetic particle diffusion coefficients, and (4) shock acceleration in a partially ionized medium. The study will develop models addressing these points, and investigate on the basis of analytical and numerical techniques. He will derive models at both a test particle and self-consistent level. Detailed modeling will be guided and complemented by multi-dimensional (1-, 2-, and 3-D) hybrid plasma simulations. The investigator hopes these studies will advance our understanding of the origin and acceleration of energetic particles and the nature of collisionless shocks.
