Overview of magnetic properties at the base of impulsively heated loops. Panel a: number of heating events for each type of magnetic structure at the footpoints of hot loops. Only those events with significant minor polarity field within a 5.4 Mm circle about the centroid of the detected UV ratio patches, associated with hot loops, are counted as mixed-polarity cases. For mixed event, area-normalised distribution of the minimum distance of the minor polarity field from the centroid of the patch detected in the UV ratio maps is plotted in panel b. Panel c: histogram of the rate of change of magnetic flux, separately for dominant (black) and minor (blue) magnetic polarities, for events labelled as mixed. See Sect. 4.1 for discussion.