Auroras (or aurorae) are natural different colored 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.
It often appears as a greenish glow (or sometimes a faint red), as if the sun were rising from an unusual direction. The aurora borealis is also called the northern lights, as it is only visible in the North sky from the Northern Hemisphere. The aurora borealis most often occurs from September to October and from March to April.
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 (at altitudes above 80 km). When the trapped magnetic field of the solar wind is favourably oriented (principally southwards) it reconnects with that of the earth and solar particles then enter the magnetosphere and are swept to the magnetotail. Further magnetic reconnection accelerates the particles towards earth.(from www.wikipedia.org)
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