Full disk images of the Sun in the 211 Å waveband taken by SDO/AIA with the corresponding photospheric magnetic field overlaid from SDO/HMI. Panel a: coronal emission and surface magnetic field near the beginning of CR 2158, where the black box highlights a large AR complex containing ARs 12235, 12237 and 12242. The image in panel b is taken at the end of CR 2158 after the large AR complex has rotated behind the limb and an eruption occurs close to the southern polar coronal hole. Red (blue) contours represent positive (negative) magnetic field values saturated at ±500 G.