Temporal evolution of plasma mixing, current density, and X-points. The bottom and top shear layers (y_sh, 1, solid; y_sh, 2, dashed) are indicated in all panels. Top panel: percentage of mixed plasma, $\stackrel{\sim }{n}/n_0$, for electrons (blue) and ions (red). Middle panel: maximum absolute out-of-plane current density, |J_z/(n₀q_ic)|,  for electrons (blue) and ions (red). Bottom panel: number of X-points in each shear layer.