Panels a)−c): NVST Hα images displaying the light wall one hour earlier than in Fig. 1. Panels d)−f): a series of IRIS 1400 Å images showing the light wall. The green curve in panel f) is the contour of a brightening patch, and the white curve in panel c) is the duplication of the patch contour here. The light walls in white dashed windows are sharpened. Panels g): Hα brightness along curve A–B in panel a). Panels f): Hα (blue curve) and 1400 Å (red curve) brightness within the arc-sector domain C–D in panels b) and e), respectively. An animation of the 1400 Å and the Hα images is available.