STEVE
Definition
A narrow mauve-purple ribbon of light that appears equatorward of the main aurora — technically not a classic aurora.
In plain language
Citizen scientists photographing strange purple arcs helped discover STEVE (Strong Thermal Emission Velocity Enhancement) — a thin glowing river of hot gas flowing westward, often with a green "picket fence" beneath it.
The science
STEVE corresponds to a subauroral ion drift: a fast (multiple km/s), hot plasma stream whose optical emission arises from heating rather than typical particle precipitation, frequently accompanied by structured green emission.
Why it matters for aurora viewing
If you shoot auroras from mid-latitudes, you may capture STEVE south of the main display — report it; the phenomenon is still actively studied.
See this in action on tonight's data.