Wave Activities Throughout a Low-Mach Number Quasi-Parallel Shock: 2-D Hybrid Simulations

In this paper, two-dimensional hybrid simulations are used to study wave excitation and evolution throughout a low-Mach number quasi-parallel shock. Simulation results show that quasi-parallel fast magnetosonic waves, ion Bernstein waves with harmonics and possible Alfven/ion cyclotron waves can be excited in the upstream region, and their small phase velocities compared to injected flow velocity results in the convection to the shock front where they are mode converted into several groups of downstream waves, including Alfven waves along the directions parallel to downstream average magnetic fields and perpendicular to the shock normal, the quasi-perpendicular kinetic slow waves and possible kinetic Alfven waves. We suggest that downstream Alfven waves originate from the mode conversion of upstream quasi-parallel fast magnetosonic waves with left-hand polarization in the downstream rest frame under helicity conservation, while the downstream left-hand polarized kinetic slow waves and right-hand polarized kinetic Alfven waves can be from the upstream quasi-perpendicular ion Bernstein waves.