IRIS maps of observation #10 in Table 1. The left panel displays the photospheric continuum map normalized to the average quiet Sun intensity. Theright panel shows the logarithm of the intensity of the Si iv 140.3 nm line measured with a Gaussian fit (see Sect. 2.2 for more details). The 280 nm and silicon masks of the two LBs are marked on the corresponding panels. Both maps were clipped for a better visibility. The widths of the LBs are comparable in the photosphere and the TR. We note the relative shift of the LBs in the two maps. The solar limb is toward the left.