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What is an aurora

09-21-2011 13:44 BJT

An aurora is a natural light display in the sky particularly in the high latitude (Arctic and Antarctic) regions, caused by the collision of energetic charged particles with atoms in the high altitude atmosphere (thermosphere). The charged particles originate in the magnetosphere and solar wind and are directed by the Earth's magnetic field into the atmosphere. Aurora is classified as diffuse or discrete aurora. Most aurorae occur in a band known as the auroral zone which is typically 3°to 6°in latitudinal extent and at all local times or longitudes. The auroral zone is typically 10°to 20°from the magnetic pole defined by the axis of the Earth's magnetic dipole. During a geomagnetic storm, the auroral zone will expand to lower latitudes.

An aurora is a natural light display in the sky particularly in the high latitude (Arctic and Antarctic) regions, caused by the collision of energetic charged particles with atoms in the high altitude atmosphere (thermosphere).

In northern latitudes, the effect is known as the aurora borealis (or the northern lights), named after the Roman goddess of dawn, Aurora, and the Greek name for the north wind, Boreas, by Pierre Gassendi in 1621. Auroras seen near the magnetic pole may be high overhead, but from farther away, they illuminate the northern horizon as a greenish glow or sometimes a faint red, as if the Sun were rising from an unusual direction. The aurora borealis most often occurs near the equinoxes.

Its southern counterpart, the aurora australis (or the southern lights), has almost identical features to the aurora borealis and changes simultaneously with changes in the northern auroral zone and is visible from high southern latitudes in Antarctica, South America and Australia.

Editor:Zheng Limin |Source: CNTV.CN

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