Overview of AR 12665 and impulsive heating events observed therein. Upper panel: three-channel composite map of the AR observed with SDO/AIA on 2017 July 11. The EUV emission recorded by three filters, AIA 171 Å (green), AIA 193 Å (blue), and AIA 94 Å Fe XVIII proxy (red), highlight various regions in the AR. The core of the AR is marked by a white rectangle. Lower panel: time series of core-integrated Fe XVIII EUV emission (black curve) for a period of 34 h. The blue curve represents the time series of solar disk integrated GOES 1−8 Å X-ray flux. Various vertical lines mark local peaks identified in the Fe XVIII light curve. Based on corresponding SDO/HMI observations, the solid vertical lines mark mixed polarity events (i.e. when at least one footpoint of the brightening loops had a mixed polarity), dashed lines identify unipolar events. These vertical lines are colour-coded with the degree of photospheric magnetic flux imbalance. Any Fe XVIII peak entirely within the grey shaded band is not considered in our analysis. See Sect. 2 and Appendix A for details.