Natural Phenomenon

Aurora is a phenomenon of light emission on burning layers of a planet's ionosphere as a result of the interaction between the magnetic field of the planet owned by charged particles emitted by the Sun ( the solar wind ) . The solar wind is a stream of electrons and protons that apart from the sun due to the high kinetic energy that has both particle and the temperature of the sun . The flow of the solar wind particles trapped in Earth's magnetic field , some of these particles leads to a polar earth with growing speed . The collision between these particles and the atoms contained in the Earth's atmosphere releases energy that causes the formation of polar auroras on earth that looks like a big circle around the pole . Hence aurora more frequent and brighter shine when the sun is most active producing Corona Mass Ejection which led to increased intensity of the solar wind .

The energy released when the particles collide can be seen visually by the color of different light . The colors seen depend on the height and type of molecules present . At altitudes above 300 km the particles collide with atoms of hydrogen cause auroras reddish light color . Altitude of 140 km , collisions with oxygen molecules cause the aurora blue or purple light . Altitude of 100 km , the particles collide with oxygen and nitrogen atoms cause green or pink light. On Earth , auroras occur in the area around the North Pole and South magnetic poles . Aurora that occurs in the northern region known as the Aurora Borealis , which is named after the Goddess of Dawn Rom , Aurora , and the Greek name for north wind , Boreas . This is because in Europe , the aurora often looks reddish in the northern horizon as if the sun will rise from that direction . Aurora borealis always occurs between September and October and March and April . The phenomenon of the aurora in the south , known as the Aurora Australis has attributes that serupa.But sometimes auroras appear at the top of the mountain in a tropical climate.

Magnetism of the earth is the appearance of the aurora in the polar regions . Suppose a charge with a certain velocity into the area containing the magnetic field at an angle that is not perpendicular to the magnetic field . Shape of the particle turns into a spiral trajectory . Earth has a magnetic field with a direction out of the south pole ( geographic north pole of the earth ) and the entrance to the north ( south geographic pole of the earth ) . when charged particles from outer space enter earth with a certain angle , then the particles will move towards and across the Earth's poles . As long as the particles moving in a spiral trajectory , the particle has acceleration that emit electromagnetic waves . As it approaches the Earth's poles , the concentration of particles are large and electromagnetic waves very large and can be observed in the sky the earth's poles .

source: http://diwanfisika.blogspot.com/2012/03/terjadinya-aurora-di-langit-yang-indah.html