AN AMAZING SHOW or the AURORA BOREALIS

The aurora borealis, also called the Northern Lights, is a multi-colored brilliant light show in the Earth's atmosphere that is caused by the collision of gas particles in the Earth's atmosphere with charged electrons from the sun's atmosphere. The aurora borealis is most often viewed at high latitudes close to the magnetic north pole but during times of maximum activity they can be viewed very far south of the Arctic Circle. Maximum auroral activity is rare however and the aurora borealis is normally only seen in or near the Arctic Circle in places like Alaska, Canada and Norway.

In addition to the aurora borealis in the northern hemisphere there is also the aurora australis, sometimes called the Southern Lights, in the southern hemisphere. The aurora australis is created the same way as the aurora borealis and it has the same appearance of dancing, colored lights in the sky. The best time to view the aurora australis is from March to September because the Antarctic Circle experiences the most darkness during this period. The aurora australis is not seen as often as the aurora borealis because they are more concentrated around Antarctica and the southern Indian Ocean.

The aurora borealis starts with the Sun. It occurs when highly charged particles from the sun's atmosphere move into the Earth's atmosphere via solar wind. They are pulled toward the Earth's poles by its magnetic force. While moving through the atmosphere the sun's charged particles collide with the oxygen and nitrogen atoms found in the Earth's atmosphere and the reaction of this collision forms the aurora borealis.

As the electrons enter the earth's upper atmosphere, they will encounter atoms of oxygen and nitrogen at altitudes from 20 to 200 miles above the earth's surface. The color of the aurora depends on which atom is struck, and the altitude of the meeting.

·   Green - oxygen, up to 150 miles in altitude

·   Red - oxygen, above 150 miles in altitude

·   Blue - nitrogen, up to 60 miles in altitude

·   Purple/violet - nitrogen, above 60 miles in altitude

All of the magnetic and electrical forces react with one another in constantly shifting combinations. These shifts and flows can be seen as the auroras "dance," moving along with the atmospheric currents.

According to the Northern Lights Centre, green is the most common color for the aurora borealis, while red is the least common.

(source: http://geography.about.com/od/physicalgeography/a/Aurora-Borealis-Or-Northern-Lights.htm)

Here you are two videos to enjoy them. Hope you like.