Monday, October 8, 2007

Aurora Borealis - Gift From The Sun

Long ago,some Asians thought the lights were dragons battling in the sky. Russians thought that it meant the spirits were lighting the way for a new birth of a child. To some Scandinavians, the auroras indicated a change of luck, good to bad, bad to good. American Indians thought that the red auroras were fires of enemies ready to battle and white auroras the torches of spirits fishing at night. New Zealand Natives considered auroras as campfires of lost souls. Other stories said that auroral displays were for reminding them of their creator or to announce the end of the world. Fifty years ago people believed that auroras were nothing but reflecting light from the sun or moon on the ice or from crystals in the atmosphere. In 1619, Galileo named the glow in the sky "Aurora" after the Roman goddess of the dawn. He mistakenly believed the glow was a reflection of the dawn. He was wrong, but the name stuck.

So, what are Auroras?

Aurora Borealis is celestial phenomenon of bands, curtains or streamers of coloured light that appear in the sky predominantly in the Arctic and Antarctic regions of the earth.
The lights by the North Pole are now called the Aurora Borealis - Northern lights. The South Pole lights are called the Aurora Austrealis - Southern lights. Not many people can see the Southern lights. It wasn't until 1773 when James Cook reported he saw them on a voyage in the South Seas, and it became known that the South Pole had auroras. Usually the North and South Poles auroras happen at the same time, and when they do, they have the same exact patterns, only reversed, like a mirror. Now that, you have to admit, is pretty cool!

Auroras are gift from the sun.
The sun gives off high-energy charged particles (also called ions) that travel out into space at speeds of 300 to 1200 kilometres per second. A cloud of such particles is called a plasma. The stream of plasma coming from the sun is known as the solar wind. As the solar wind interacts with the edge of the earth's magnetic field, some of the particles are trapped by it and they follow the lines of magnetic force down into the ionosphere, the section of the earth's atmosphere that extends from about 60 to 600 kilometres above the earth's surface. When the particles collide with the gases in the ionosphere they start to glow, producing the spectacle that we know as the auroras. The array of colours consists of red, green, blue and violet.

The Northern Lights are constantly in motion because of the changing interaction between the solar wind and the earth's magnetic field. The solar wind commonly generates up to 1000,000 megawatts of electricity in an auroral display and this can cause interference with power lines, radio and television broadcasts and satellite communications


dump said...

Sick - hope one day to see with my own eyes.