Short · Space
Why are the northern lights green?
Oxygen emits green around roughly 100–250 km. Its slower red glow survives higher up, while energetic electrons can add nitrogen purple and pink lower down.
Try it yourself
Opens Aurora Chamber. Change the same thing yourself.
Transcript
Why are the northern lights mostly green, with red on top? It's oxygen, glowing at two heights. Electrons from space, steered by Earth's magnetic field, crash into the air near the poles about one hundred kilometers up, and oxygen there glows green. Above about two hundred kilometers, the air is so thin that oxygen has time to release a slower glow: red. Now raise the electrons' energy. They plunge deeper, to nitrogen, adding a purple and pink fringe at the bottom. Try it yourself at Explainer Tools dot com.