Electron mixing fraction (F_e) in the lower shear layer during the nonlinear phase. From left to right, the rolled-up vortices at $t=389{\mathrm{\Omega }}_{\mathrm{c},\mathrm{i}}^{-1}$, their merging at $t=501{\mathrm{\Omega }}_{\mathrm{c},\mathrm{i}}^{-1}$, and the late nonlinear stage at $t=946{\mathrm{\Omega }}_{\mathrm{c},\mathrm{i}}^{-1}$ are shown. White lines trace the in-plane magnetic field. In the right panel, two ejected plasma parcels (P1: red; P2: blue) are highlighted.