Why the aurora has different colours
The colours of the aurora come from atoms and molecules in the upper atmosphere, each glowing at its own wavelength when struck by energetic particles.
Green
The familiar green comes from oxygen atoms at roughly 100–250 km altitude, emitting at 557.7 nanometres. It is the brightest auroral colour and the one our eyes are most sensitive to at night.
Red
Oxygen higher up, above about 250 km, emits deep red light at 630 nanometres. It is fainter and slower to appear, and it is what people far from the pole often see during big storms: a red glow high above the horizon, because the green lower part is below their horizon.
Pink, blue and purple
Molecular nitrogen produces blue and violet light and, at the lower edge of bright, fast-moving curtains, a pink or magenta fringe. These colours are strongest during intense activity.
Why cameras see more
In dim light the eye relies on rod cells, which do not see colour well. A faint aurora can look grey or milky to the eye while a camera, collecting light for several seconds, records vivid green. Bright displays are clearly coloured to the eye as well.
STEVE and other oddities
STEVE is a narrow purple-white ribbon, sometimes with green 'picket fence' streaks, seen at lower latitudes than the normal oval. It was described with help from citizen scientists in 2016–2018 and is not caused in the same way as ordinary aurora. Proton aurora, another type, is broad and diffuse and usually too faint to see with the naked eye.
Last reviewed 15 October 2026