Earth's atmosphere creates glow-in-the-dark light show

Sandrine Ceurstemont, editor, New Scientist TV

Auroras aren't the only light show shining above the Earth. The atmosphere itself can also produce light, creating rings of colour that glow in the dark.

Now neuroscientist and moviemaker Alex Rivest has produced a new video that illustrates the phenomenon, called airglow. Atoms and molecules, excited by ultraviolet radiation from the sun, emit light when they return to their ground state or when they combine due to chemical reactions to create new molecules. During the day, scattered light from the sun masks this activity, so it only becomes visible after dark.?

Different atoms and molecules are responsible for each colour. The yellow layer, which is about 5 km thick, is made up of sodium atoms from broken up meteors that radiate weakly in their excited state. Directly above, a thinner green band is visible as oxygen and nitrogen combine to form nitric oxide. A faint blue glow surrounds the green one, made up of excited oxygen molecules. Higher up, a red layer lurks due to light emissions as ozone and hydrogen combine to form excited hydroxyl radicals.

The rings are not always uniform due to gravity waves in the atmosphere. Like waves in water, they occur when stable layers of different densities are disturbed and try to regain equilibrium.

If you enjoyed this video, check out a night flight on the ISS that reveals dazzling city lights or the first observation of a space storm in the Earth's upper atmosphere.

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