Each motion or brightness change in one hemisphere is mirrored in the other, on a time scale of less than a fraction of a second. A most curious and highly controversial question involves auroral sound. Although I've never heard one, my wife has and so have several scientists I know. Some reports of hearing noises associated with auroral displays may be erroneous impressions, but I am convinced many others are not. Hundreds of written reports indicate noises are sensed when a particular type of fast-Aurora is nearly overhead.
Some people sense whistling and crackling noises, even when they close their eyes.
The reports of auroral sound make it certain that the unknown cause of the apparent sound is in the vicinity of the hearer, not in the Aurora itself. Most likely, the reported noises are related to electrical phenomena which accompany certain types of bright Aurora. No matter how many auroras one may have seen, a good high-latitude display, as seen in Alaska, sends tingles up the viewer's spine. The best of words and photographs fail to capture the magnificence of the high-latitude Aurora, although some of Robert Service's poetry may come close. LIKE A NEON SIGN , auroral light is produced by a high-vacuum electrical discharge.