Sky Oddities • Auroras & Plasma Phenomena • Child Pillar
STEVE is a strange purple-white arc that appears outside the usual auroral oval during geomagnetic activity. It can look like a glowing ribbon stretched across the sky, often accompanied by green picket fence structures and unusual subauroral purple emissions.
This guide explains STEVE sightings, purple arc events, green picket fence structures and subauroral purple emissions — one of the strangest modern sky phenomena hiding in plain sight above Earth.
TL;DR: STEVE Purple Arc
- STEVE stands for Strong Thermal Emission Velocity Enhancement.
- It appears as a narrow purple or mauve arc outside the main auroral oval.
- STEVE is not the same as a normal aurora, although it often occurs during geomagnetic activity.
- Green picket fence structures can appear near STEVE as vertical green streaks.
- STEVE is linked to fast ionospheric flows and subauroral heating.
- This page absorbs STEVE sightings, purple arc events, green picket fence structures and subauroral purple emissions.
What Is STEVE?
STEVE is a luminous subauroral phenomenon that appears as a narrow purple or white-purple ribbon across the night sky. The name stands for Strong Thermal Emission Velocity Enhancement.
Unlike ordinary auroras, STEVE usually appears outside the main auroral oval. It is associated with fast ionospheric flows, heating and unusual subauroral conditions rather than classic auroral particle precipitation alone.
In simpler terms: STEVE looks like an aurora, behaves differently, and has spent years confusing both skywatchers and scientists — very efficient work for a purple line in the sky.
Why STEVE Looks Like a Purple Arc
STEVE is best known for its long, narrow purple or mauve arc. This arc can stretch across a large portion of the sky and may appear smooth, bright and sharply defined compared with ordinary auroral curtains.
The purple color is linked to emissions produced under unusual subauroral conditions. STEVE can also appear whitish, pinkish or lavender depending on brightness, camera sensitivity and atmospheric conditions.
Old articles about purple sky arcs, mysterious purple auroras or STEVE-like ribbons should redirect here when the core topic is the purple STEVE arc.
Green Picket Fence Structures
Some STEVE displays include a green picket fence: vertical green streaks that appear near or below the purple STEVE arc.
These structures look like glowing fence posts rising from the horizon. They are visually linked to STEVE events but may involve different physical processes than the purple arc itself.
This page should absorb older posts about:
- green picket fence auroras
- green vertical streaks near STEVE
- STEVE with green structures
- purple arc and green fence displays
Subauroral Purple Emissions
Subauroral purple emissions occur outside the normal auroral oval and are part of what makes STEVE so unusual. These emissions reveal that visible sky glows can happen in regions not usually associated with classic auroras.
These events may be seen as:
- thin purple arcs
- mauve sky ribbons
- lavender bands
- white-purple subauroral glows
- purple emissions photographed during geomagnetic activity
This makes STEVE an important bridge between aurora science, ionospheric physics and strange sky phenomena.
STEVE vs Ordinary Auroras
| Feature | STEVE | Ordinary Auroras |
|---|---|---|
| Typical Color | Purple, mauve or white-purple | Green, red, purple, blue or pink |
| Shape | Narrow arc or ribbon | Curtains, rays, arcs and coronas |
| Location | Subauroral region | Main auroral oval |
| Process | Fast ionospheric flows and heating | Particle precipitation into the upper atmosphere |
STEVE Sightings
STEVE became widely known thanks to skywatchers and citizen scientists who repeatedly photographed the purple arc and noticed that it did not behave like ordinary auroras.
STEVE sightings are often reported:
- during geomagnetic activity
- near but outside normal aurora zones
- as a long purple arc stretching across the sky
- with or without green picket fence structures
- from mid-latitude regions where auroras are less common
This child pillar is the best 301 target for old one-off STEVE sightings and purple arc events.
What Belongs Elsewhere?
This page is specifically for STEVE purple arc events and associated green picket fence structures. Keep related but different topics in their canonical homes:
- General auroras → Auroras Explained
- Aurora colors → Aurora Colors Explained
- Extreme aurora outbreaks → Extreme Aurora Events Explained
- SAR arcs and stable red arcs → SAR Arcs Explained
- Solar storms and forecasting → Space Weather cluster
FAQ: STEVE Purple Arc
What is STEVE?
STEVE stands for Strong Thermal Emission Velocity Enhancement and appears as a narrow purple-white arc in subauroral regions.
Is STEVE a normal aurora?
No. STEVE looks aurora-like but is linked to different subauroral processes, including fast ionospheric flows and heating.
Why is STEVE purple?
STEVE’s purple or mauve color is linked to unusual emissions produced under subauroral ionospheric conditions.
What is the green picket fence?
The green picket fence is a set of vertical green streaks sometimes seen near STEVE during geomagnetic activity.
Where do STEVE sightings belong?
Old posts about STEVE sightings, purple arc events, green picket fence structures and subauroral purple emissions should redirect to this page.
