Ion dynamics in quasi-perpendicular nonstationary shocks: comparison between MMS observations and hybrid modeling

Reflection of a fraction of incoming ions is a vital dissipation mechanism for super-critical shocks. Such reflected ions provide a significant contribution to the downstream ion temperature increase. Understanding ion dynamics is crucial for the characterization of the shocks. It is needed to provide an equation of state that connects the upstream and downstream parameters for given shock parameters. The reflection depends on the detailed structure of the electromagnetic fields in the shock transition region. The ion-scale structure is strongly affected by the shock non-stationarity. To characterize the spatiotemporal evolution of the shock structure and ion reflection, we combine observations of several in-situ shock events by MMS with hybrid simulations performed for the specific parameters of the observed shocks. We find that the ion reflection is strongly affected by the structure imposed by the ripples. The reflection is very patchy, with regions of strong and weak ion reflection.