Top row: evolution of a FOV around two SSUBs (including the event plotted in the top left panel of Fig. 6) at − 0.217 Å into the blue wing of the Ca ii 8542 Å line. Each column is separated in time by about 29 s. Middle row: same as the top row but for the Ca ii 8542 Å line core. Bottom row: same as above but for 0.217 Å into the red wing of the Ca ii 8452 Å profile. Arrows indicate the positions of the co-spatial short dynamic fibrils. The SSUBs are clearly visible in the fourth and sixth columns of the − 0.217 Å and line core images (indicated by white arrows in the fourth and sixth frames of the top row).