A new (or at least previously unrecorded) type of aurora has been identified, one that looks more like rippling sand dunes than the vertical curtains of light usually seen.
The current hypothesis is that it occurs when an atmospheric wave gets trapped in layers of the mesosphere, causing it to propagate horizontally, and that wave intersects with the charged particles that produce an aurora.
https://www.syfy.com/syfy-wire/citizen-scientists-discover-a-new-type-of-aurora-dunes