Investigating the interactions of alpha particles in collisionless oblique heliospheric shocks

<p>Heliospheric shocks associated with interplanetary coronal mass ejections (ICMEs) were observed by Wind, and DSCOVR at L1, STEREO spacecraft at ~1AU, and recently by the Parker Solar Probe in the inner heliosphere. The magnetic structure and the downstream magnetic oscillations were detected by Wind with 10.9 samples/s and DSCOVR with 50 samples/s. However, the velocity distributions of the protons are available at much lower cadence, and the potentially important interaction between &#160;the alpha particles and &#160;the heliospheric shocks are difficult to obtain directly from present data.&#160;Since the alpha particles in the solar wind are the second most abundant ion that can carry significant energy, momentum and mass flux of the solar wind, the alphas can significantly affect the propagation of these shocks. Recently, using hybrid-(PIC) models we studied the effects of alpha particles on the structure and magnetic oscillations of oblique high Mach number heliospheric shocks, and found that the magnetic and density structures of these shocks are significantly affected by the alpha particles with typical solar wind relative abundances. Here, we extend the study and report the results of new hybrid models of oblique shocks guided by observations. We investigate the typical observed relative solar wind abundances of alphas, Mach numbers, and shock normal directions, and compare the results for the various shock parameters. We model the effects of alpha particles properties on the shock ramp, wake, and downstream oscillations and study the properties of proton and alpha particle velocity distribution functions (VDFs) and the kinetic waves downstream of the shocks in the inner heliosphere. We expand the model and study for the first time the effects of relative streaming of proton-alpha ion populations as well as the ion anisotropies on the shock propagation. We investigate the effects of the ion kinetic properties on the heliospheric shock structures and discuss how the modeling results can improve the interpretation of spacecraft observations of these shocks.&#160;</p>