The effects of Alpha Particles on Oblique High Mach Number Heliospheric Shocks

Spacecraft observations of shocks often show oscillations in the magnetic field and density both, upstream and downstream. The magnetic oscillations of oblique collisionless shocks were detected by DSCOVR/MAG with high temporal resolution of 50 samples/s. The density oscillations associated with the shocks are seen by DSCOVR and Wind in protons and in α particle by Wind (with lower temporal resolution). Recently, we have investigated low Mach number low-β oblique shock oscillations using satellite data and 2.5D hybrid modeling with electrons modeled as fluid and ions modeled as particles. In particular we found that α particles may affect considerably the downstream oscillations and the shock structure. Here, we extend our previous study to high Mach number shocks (M>3) and investigate a range of plasma β values in the β<~1 range and compare the results to available observations of similar shocks. Using the 2.5D hybrid model we find that high Mach number shocks exhibit time-dependent corrugation (rippling) of the shock front. We investigate the effects of α particle abundances and other kinetic properties on the rippling and the non-stationarity of the oblique high Mach number shocks. We model the structure and the evolution of the proton and α particle velocity distributions in various locations in the downstream region of the shocks and discuss the observational implications.