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aurora australis
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aurora australis

  the luminous, radiant emission from the upper atmosphere seen on clear winter nights — usually above the south magnetic pole
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Strongly Associated with:   aurora, aurora borealis
Its northern counterpart, aurora borealis, has similar properties.
Auroras are now known to be caused by the collision of charged particles (ions (+) (-) ) found in the magnetosphere, with atoms in the Earth’s upper atmosphere (at altitudes above 80 km). These particles travel into space with speeds of 300 to 1200 kilometers per second. A cloud of these particles is called plasma, and a stream of plasma coming from the sun is called solar wind. These charged particles are typically energized to levels between 1 and 15 keV and, as they collide with atoms of gases in the atmosphere, the atoms become excited. Shortly afterwards, the atoms emit their gained energy as light (see Fluorescence).  (retrieved 6/08)
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Associated words [difficulty]:   aurora australis , aurora [4] , aurora borealis [7] , aura [1] , aurora [4] , aurora borealis [7]
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Most commonly used in these subjects:   Sports, Science
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