Friday, October 24, 2008

Aurora borealis

Aurora borealis is a luminous phenomenon which consists of streamers of light appearing in the upper atmosphere of the northern hemisphere, near the polar regions. It is caused by the emission of light from atom excited by electrons accelerated along the planet's magnetic field lines. The aurora borealis is also called the northern polar lights, for it is only visible in the sky from the northern hemisphere, the chance of visibility increasing with proximity to the northern magnetic pole. The aurora borealis was named after Roman goddess of dawn, Aurora, and the Greek name for the north wind, Boreas.