When a piston drives a shock in a multicomponent plasma, residual separation of the ion species persists close to the piston-plasma boundary, long after the shock has propagated away from the boundary and has reached a (nearly) steady-state solution. This effect is observed in hybrid particle-in-cell simulations with two kinetic ion species and fluid electrons. It is a consequence of the different dynamics experienced by ions of different mass and charge-to-mass ratio and must be taken into account to properly model the physics of species separation in collisional plasma shocks.
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