After decades of research, our understanding of the aurora is disturbingly incomplete. One long-held belief, that aurorae are much more common following each peak in the 11-year solar cycle, has now been overturned. It is also becoming more certain that discrete aurorae occur more often above dark regions of the atmosphere than above sunlit regions. Both of these discoveries support the idea that aurorae are discharge phenomena, but make it hard to explain what sort of electrical generator could be responsible.
