Illustration of the propagation of the EB analyzed in Case Study I for both the blue (−1 Å; top) and red (+1 Å; middle) wings of the Hα line profile, as well as the SDO/AIA 304 Å filter (bottom). The almost northward propagation of this event appears to be parallel to the near-by penumbra and follows the bright track evident in the third panel. In the second panel for each wavelength, three small sub-structures are highlighted with arrows. The line wings are originally sampled at 7:29:54 UT and each subsequent image is separated by 146.3 s.