The left-hand column shows the evolution of the inner ∼200 km of the simulation domain for model L_2.4. The colour map depicts the electron fraction, Y_e, with velocity vectors overlaid; the black lines indicate Z= 0. The colour map for the middle column depicts density. The pink curve shows the location of the shock. Exterior to the shock, the flow is radially inward. The right-hand column panels show the entropy evolution of the explosion. The steep entropy jump just interior to the shock depicts the region where nucleons are re-associated into nuclei and α particles. At 707 ms after bounce, the PNS wind is seen as the dark blue region interior to the shock in the middle panel. The supernova explosion primarily occurs in the −Z direction, while the PNS recoils in the +Z direction. At ∼800 ms after bounce, the PNS has largely decoupled from the surrounding material, but is still being accelerated by the gravitational pull of slow-moving ejecta in the +Z direction (see Fig. 3).