Space-time diagrams along the vertical direction. These show the horizontally averaged vertical profile of the respective quantity as a function of time. From top to bottom: Evolution in EUI 174 Å (a–b), Hinode/XRT (c–d), and in heating rate (e–f). Left: Original value of the emissivity (a, c) and heating rate (e). Right: Respective running difference images (with a time delay of 10 s) simply to highlight the temporal changes. The dashed lines indicate apparent speeds of 184 km s⁻¹ (a–b) and 504 km s⁻¹ (c–f). See Sect. 3.1.