What Causes the Different Colours of the Aurora?

Overview

The aurora's colours come from which gas the solar particles hit, and at what altitude. Here's the quick science.

Green

The most common colour, from oxygen at around 100–150 km — the most energetic, frequent reaction.

Red, blue & violet

Red comes from oxygen high above 200 km (rarer); blue and violet come from nitrogen at lower altitudes, often at the edges of strong displays.

Seeing them

Strong displays can show several colours at once. To the eye, green is clearest; cameras reveal more. See our colours guide.

Frequently Asked Questions

Why are the Northern Lights green?

Green comes from oxygen atoms around 100–150 km up — the most common and energetic aurora reaction, so green is what you see most often.

What makes the aurora red or purple?

Red comes from oxygen high above 200 km, while blue and violet come from nitrogen at lower altitudes. These appear during stronger geomagnetic activity.

Can the aurora be multiple colours at once?

Yes — during strong displays you can see green with pink, violet or red edges simultaneously, filling much of the sky.

What Causes the Aurora's Colours?

Overview

Green

Red, blue & violet

Seeing them

Frequently Asked Questions

See Every Colour of the Sky