Aurora Borealis

Aurora Borealis - 3 at Fairbanks - Sep. 29, 2006

"The name
The northern lights have had a number of names through history. The scientific name for the phenomena is Aurora Borealis, which is Latin and translates into the red dawn of the north. It was the Italian scientist Galileo Galilei (1564-1642) who first used the expression. On the latitude where Galileo was living, northern lights consist of mainly red colour.

What causes them?
Northern lights originate from our sun. During large explosions and flares, huge quantities of solar particles are thrown out of the sun and into deep space. These plasma clouds travel through space with speeds varying from 300 to 1000 kilometers per second.

But even with such speeds (over a million kilometer per hour), it takes these plasma clouds two to three days to reach our planet. When they are closing in on Earth, they are captured by Earth's magnetic field (the magnetosphere) and guided towards Earth's two magnetic poles; the geomagnetic south pole and the geomagnetic north pole.

On their way down towards the geomagnetic poles, the solar particles are stopped by Earth's atmosphere, which acts as an effective shield against these deadly particles.

When the solar particles are stopped by the atmosphere, they collide with the atmospheric gases present, and the collision energy between the solar particle and the gas molecule is emitted as a photon - a light particle. And when you have many such collisions, you have an aurora - lights that may seem to move across the sky.

- quoted from www.northern-lights.no";