Co-aligned images of the multiwavelength observations. Panels a)–f): the aligned Hα, magnetogram, and continuum intensity images. Middle panels are the corresponding subsets of the top panels in the blue FOV. Panels g)–i): in 304 Å images, bright mass motion (green arrows) swept the periphery (denoted by white dashed-dotted lines in panel g)) of the arch filament from the north to the south and even reached the very close vicinity of the LB (the yellow arrow in panel i)) in the blue FOV. A red box in panel b) denotes the FOV of subsequent Figs. 2−5. Green dotted lines “A–B” indicate the long axis of the arch filament. The red arrow in panel f) denotes the LB discussed in this work. An animation of the Hα, 304 Å, and HMI continuum intensity channels shown in this figure is available in the online edition.