Fig. 6

(a–h) Snapshots by the digital camera from 22:40:00 to 22:47:00 UT. The top is north, and the right is east. Several purple patches appeared poleward of the wavy discrete aurora. The white and yellow arrows guide the eastward propagation of the patches. The green arrows guide the eastward propagation of the wavy structure of the discrete aurora. i–l All-sky images observed from OMTI at the closest time to (b). The measured wavelengths are at the top of each panel. The recorded times are at the bottom. The color scale indicates the Rayleigh value. The white and yellow arrows indicate that the purple patch has an emission at all four wavelengths, including the background line at 572.5 nm