Interaction of pickup ions with quasi-parallel shocks

We have performed a number of numerical experiments to study the interactio n of interstellar pickup protons and helium ions with quasi-parallel statio nary (bow) shocks and interplanetary traveling shocks. The collisionless sh ocks are modeled by the hybrid simulation method which treats the ions as m acroparticles and the electrons as a massless background fluid. Solar wind protons, alpha particles, pickup H+ and He+ are included self-consistently The pickup ion distributions are modeled as spherical shells in velocity sp ace convected with the solar wind. Pickup ions are rather efficiently refle cted at both types of shocks. The reflection coefficient, measured as the r atio of incident 50 reflected ions, is more than one order of magnitude lar ger than the reflection coefficients for either solar wind protons or alpha particles, and is of the order of 30%. We have found that at high Mach num ber shocks pickup ions can reach many tens to over hundred times the plasma ramming energy in essentially one shock encounter. The reflected pickup io n distributions have a pancake-type shape in velocity space.