Kinetic Study of Quasi-Parallel Shock formation and particle acceleration

Quasi-parallel collisionless shocks (in which the shock normal is approximately parallel to the background magnetic field) are believed to be the most efficient accelerators in the universe. Compared to quasi-perpendicular shocks, quasi-parallel shocks are more difficult to form in the laboratory and to simulate because of their large spatial scales and long formation times. Our 2-D particle-in-cell simulations show that the early stage of quasi-parallel shock formation is achievable at the National Ignition Facility, and that particles accelerated by diffusive shock acceleration are expected to be observable experimentally. Repetitive ion acceleration by crossings of shock front, a key feature of DSA, is seen in the simulations. Collisionless dissipation mechanisms and particle spectra for different magnetic field angles to the shock normal will be presented.