Categorization of the y/t − z/t plane in terms of large-time expectations for the morphological features of impulsive kink motions. The bordering straight lines are determined by the limiting behavior of the group velocities as derived from Figs. 3 and 6. Line I₊ pertains to B₀-same-side fundamental modes, while line I₋ (II₋) pertains to B₀-straddling modes associated with the transverse fundamental (first overtone). Four sectors result. Different morphological features are expected for different sectors, the difference being particularly pronounced when line I₋ is crossed. One representative point in each sector (marked P₁ to P₄) is selected for further quantitative analysis (see text for more details).