Impulsive heating in the core of AR 12692. Panels a–g: similar to their counterparts in Fig. 2. Panels h and i: time series of light curves from footpoint regions E and W1 (marked in panel a). Panel j: an IRIS Si IV 1394 Å raster map in an inverted colour scheme. The overlaid circle is roughly at the same location as in panels a–d. Footpoint regions E-R-W1 are marked. A 10 Mm scale is overlaid. The IRIS SJI 2796 Å light curve from footpoint-R (magenta box) is displayed in panel e. SJI 1400 Å light curves from footpoints E and W1 (green boxes in panel j) are shown in panels h and i. Panels k–m: Si IV, Mg II k, and Mg II triplet spectral profiles (footpoint-R in magenta-plus; footpoint-E in green-plus; footpoint-W in green-asterisk; average quiet Sun profiles in black; in panel k the quiet Sun profile is multiplied by ten and the dotted line identifies a Ni II absorption profile). The timestamps of the spectral profiles in UT are given in panel j. AIA data are plotted at their native cadence (EUV at 12 s and UV at 24 s). Animation of panels a–g is available online. See Sects. 2, 3.2 and Appendix A for details.