Morphological evolution of the lower (y = y_sh, 1) and upper (y = y_sh, 2) shear layers at t = 445, 501, 723, and $946{\mathrm{\Omega }}_{\mathrm{c},\mathrm{i}}^{-1}$ during the nonlinear stage of the KHI. Each panel shows a region around each shear that is 100 × 150 d_i². The color bar shows $\stackrel{\sim }{n}/n_0$ in percentages, which describes the mixing of the two plasma regions normalized to the initial value (see text). The top two rows show the ion mixing (a–d upper shear, e–h lower shear), and the bottom two rows show the electron mixing (i–l upper shear, m–p lower shear).