Spatial evolution of a compact UV burst and the surrounding magnetic environment as seen with IRIS and SDO/HMI. Panels a and d show two SJI 1400 Å images separated by 50 min that mainly outline chromospheric and transition region features. Panels b and e show co-temporal SJI 2832 Å images displaying photospheric granulation. Co-temporal HMI line-of-sight magnetic field maps saturated at ± 250 G are plotted in panels c and f. The location of the compact UV burst is outlined by a white box in all the panels. Here the white box marks the sub-field of view of raster maps we used for the more detailed investigation. This sub-field of view is shown as an inset map in the left panel of Fig. 3 and in the two panels of Fig. 4. The two SJI 1400 Å images are the negatives of the square-root-scaled intensity. The vertical lines in panels b and e show the locations of the slit positions at these times. See Sect. 2.1.