Aurora Borealis Poster

Picture of Aurora taken from the Lehigh Valley in October 2003. It is unusual to see here. This was the result of a large solar flare. The red colour comes from electrons striking oxygen molecules at altitudes of 200 km to 500 km. "usual" auroras strike at 100 km (60 miles). Picture is across a pasture, facing the mountains (NE). Auroras are natural different coloured light displays, which are usually observed in the night sky, particularly in the polar zone. Some scientists therefore call them "polar auroras" (or "aurorae polaris"). In northern latitudes, it is known as the aurora borealis, named after the Roman goddess of the dawn, Aurora, and the Greek name for north wind, Boreas. Its southern counterpart, aurora australis/southern [polar] lights, has similar properties. Australis is the Latin word for "of the South". Auroras are produced by the collision of charged particles, mostly electrons but also protons and heavier particles, from the magnetosphere, with atoms and molecules of the Earth's upper atmosphere. Most originate from the sun and arrive at the vicinity of earth in the relatively low-energy solar wind.