Science guide
Aurora colours explained
Why is the aurora usually green — and sometimes red, pink or purple? Every colour is a fingerprint: it tells you which gas was hit and how high up. Here's the whole palette, and what each colour is telling you.
The short answer: colour equals altitude
When particles from the Sun hit the atmosphere, they excite atoms of oxygen and nitrogen, which release that energy as light at very specific wavelengths. Which colour you get depends on the gas and the altitude — because the thinner the air, the longer an atom can glow before it bumps into a neighbour. As a rule of thumb: low is purple, the middle is green, and high is red.
The colours, at a glance
Green
Atomic oxygen (557.7 nm)
Red
Atomic oxygen (630.0 nm)
Pink / magenta
Nitrogen, lower edge
Blue / violet
Ionised nitrogen (427.8 nm)
There's no single “yellow” emission. When a bright display mixes green and red, or several emissions overlap, the eye reads the result as yellowish or white. White also shows up simply because very bright light saturates your colour vision.
What is STEVE?
STEVE (Strong Thermal Emission Velocity Enhancement) is a narrow mauve-purple ribbon, often with a green “picket fence” of vertical bars beside it, seen at lower latitudes than normal aurora. Despite appearances it isn't a true aurora — it's a river of hot, fast-moving plasma flowing through the upper atmosphere. It was named and brought to scientists' attention by citizen-scientist aurora chasers, and it's one of the most prized sights in the sky.
Why it looks grey to your eye but colourful on camera
In the dark your vision switches to the eye's rod cells, which are far more sensitive to light but effectively colour-blind — so a faint aurora reads as pale grey or white. Only when a display is bright enough do your colour-sensing cones kick in, and green appears first. A camera has no such limit: it gathers light over several seconds and records the pinks, reds and purples your eyes simply can't register.
See the colours for yourself
Bright, colourful aurora needs an active, dark, clear sky. Our live forecast checks that for your location, the science guide explains the whole chain from the Sun, and the photography guide shows you how to capture every shade.