Fox fires
In Finnish, the northern lights are revontulet, "fox fires". Behind the name is a story about a fox, a forest and a sky set alight.
The firefox
The folklore of northern and eastern Finland has a creature called the tulikettu, the firefox: a fox whose tail twinkles with fire. In Lapland people said this fox made the northern lights. As it ran, its tail brushed against low branches and bushes and flung sparks up into the sky. In another telling, the tail sweeps snow upwards, and the flakes catch the light.
The firefox’s fur was said to glow when brushed the right way. Some stories even say its pelt was used to light gunpowder stores at night, because an open flame would have been far too dangerous.
The king of the forest
The forest the fox ran through had its own ruler. In Finnish folklore, Tapio is the spirit of the forest and the hunt, the King of the Forest (Metsän kuningas). He has a beard of lichen and eyebrows of moss, and he rules the forest realm of Tapiola with his wife Mielikki. Hunters prayed to him for luck and left him offerings of food.
Put the two stories together and the northern forest becomes a lively place: a king of lichen and moss below, and above him a sky lit by a fox’s tail.
What is really glowing
The real cause is no less remarkable. Charged particles from the Sun pour into the upper atmosphere and strike its gases, which glow as they settle back down. The colour depends on which gas is hit, and how high.
Red comes from oxygen more than 200 km up. The familiar green is oxygen too, between about 100 and 200 km. Nitrogen adds blue at similar heights, and a pinkish fringe lower still, below about 100 km. The spruce forests of Lapland sit in the dark beneath it all.
In the old story, though, the lights only happen because there are trees for the fox’s tail to brush. No forest, no fox fires.