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aurora borealis

aurora borealis (bôr´ēăl´Ĭs) and aurora australis (ôstrā´lĬs), luminous display of various forms and colors seen in the night sky. The aurora borealis of the Northern Hemisphere is often called the northern lights, and the aurora australis of the Southern Hemisphere is known as the southern lights. Each is visible over an area centering around the geomagnetic pole of its own hemisphere. The aurora borealis is said to occur with greatest frequency along a line extending through N Norway, across central Hudson Bay, through Point Barrow, Alaska, and through N Siberia. It is often visible in Canada and the N United States and is seen most frequently at the time of the equinoxes; in times of extreme activity, it may be seen in parts of the S United States. Among the most magnificent of natural phenomena, auroral displays appear in shades of red, yellow, green, blue, and violet and are usually brightest in their most northern latitudes. The aurora is seen in a variety of forms, e.g., as patches of light, in the form of streamers, arcs, banks, rays, or resembling hanging draperies. The aurora occurs between 35 mi and 600 mi (56 km–970 km) above the earth. It is caused by high-speed electrons and protons from the sun, which are trapped in the Van Allen radiation belts high above the earth and then channeled toward the polar regions by the earth's magnetic field. These electrically charged particles enter the atmosphere and collide with air molecules (chiefly oxygen and nitrogen), thus exciting them to luminosity; near the 600-mile level, the light may be given off by electrons and protons combining to form hydrogen atoms. The auroras coincide with periods of greatest sunspot activity and with magnetic storms (disturbances of the ionosphere which interfere with long-distance radio communication). Much was learned about the aurora during the 1957–58 International Geophysical Year, when it was studied intensively by means of balloons, radar, rockets, and satellites. Other planets in the solar system also have auroras.

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aurora

aurora Illumination of the sky, sometimes in brilliant colours, as a result of high-speed solar particles entering the ionosphere (at a height of 100–130 km) and releasing electrons from air molecules by excitation. The re-establishment of molecules leads to the emission of light, especially red- and green-coloured light, e.g. in arcs or bands over large areas. The effect is called ‘aurora borealis’ or ‘northern lights’ in the northern hemisphere and ‘aurora australis’ or ‘southern lights’ in the southern hemisphere. Such atmospheric disturbances occur in relation to disturbances on the Sun in the course of the sunspot cycle.

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Aurora

Aurora in Roman mythology, the goddess of the dawn, equivalent of the Greek Eos. Most of the stories about her tell of handsome men being kidnapped to live with her.

From the early 18th century, aurora has been used to designate a natural electrical phenomenon characterized by the appearance of streamers of reddish or greenish light in the sky, especially near the northern or southern magnetic pole. The effect is caused by the interaction of charged particles from the sun with atoms in the upper atmosphere. In northern and southern regions it is respectively called aurora borealis or northern lights and aurora australis or southern lights.

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aurora

au·ro·ra / əˈrôrə; ôˈrôrə/ • n. (pl. au·ro·ras or au·ro·rae / ôˈrôrē/ ) 1. a natural electrical phenomenon characterized by the appearance of streamers of reddish or greenish light in the sky, usually near the northern or southern magnetic pole. 2. [in sing.] poetic/lit. the dawn. DERIVATIVES: au·ro·ral adj.

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aurora

aurora dawn XIV; luminous atmospheric phenomenon near the poles, ‘northern lights’ XVIII; also aurora borealis (see BOREAL), so named by Pierre Gassendi in 1621. — L. aurōra (see EAST).

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aurora

aurora Sporadic, radiant display of coloured light in the night sky, caused by charged particles from the Sun interacting with air molecules in the Earth's magnetic field. Auroras occur in polar regions and are known as aurora borealis in the n, and aurora australis in the s.

http://www.sel.noaa.gov/pmap; http://www.spaceweather.com

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aurora borealis

aurora borealisAlice, chalice, challis, malice, palace, Tallis •aurora australis •Ellis, trellis •necklace •aurora borealis, Baylis, digitalis, Fidelis, rayless •ageless • aimless • keyless •amaryllis, cilice, Dilys, fillis, Phyllis •ribless • lidless • rimless •kinless, sinless, winless •lipless • witless • annus mirabilis •annus horribilis • syphilis •eyeless, skyless, tieless •polis, solace, Wallace •joyless •Dulles, portcullis •accomplice •Annapolis, Indianapolis, Minneapolis •Persepolis •acropolis, cosmopolis, Heliopolis, megalopolis, metropolis, necropolis •chrysalis • surplice • amice • premise •airmiss • Amis • in extremis • Artemis •promise •pomace, pumice •Salamis •dermis, epidermis, kermis

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