Aurora Borealis

Aurora Borealis(in north) /Aurora Australis(in south), a luminous atmospheric phenomenon that generally appear as bright colorful bands of light commonly referred to as the southern and northern lights, occur in the ionosphere. Auroras are often visible in the night sky in both the northern and southern regions of the Earth. The aurora was named after the Roman goddess of dawn, and was long thought to be produced by sunlight reflected from polar snow and ice, or refracted light much like rainbows. Auroras are caused by high energy particles from the solar wind that is trapped in the Earth's magnetic field . As these particles spiral back and forth along the magnetic field lines, they come down into the atmosphere near the north and south magnetic poles where the magnetic field lines disappear into the body of the Earth. The delicate colors are caused by energetic electrons colliding with oxygen and nitrogen molecules in the atmosphere. This excites the molecules, and when they decay from the excited states they emit the light that we see in the aurora. Alaska is by far the best place in the USA to see northern lights that too in the months of September and March, as the Earth is in the zone of maximum solar activity during that period. The aurora is most active late at night or early in the morning, when the sky is clear and the air chilly.
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Auroras (north/south polar lights; or aurorae) are natural light displays in the sky, usually observed at night, particularly in the polar zone. They typically occur in the ionosphere. They are also referred to as "polar auroras". In northern latitudes, the effect is known as the aurora borealis, and it was named after the Roman goddess of dawn, Aurora, and the Greek name for north wind, Boreas by Pierre Gassendi in 1621. The aurora borealis is also called the northern polar lights, as it is only visible in the sky from the Northern Hemisphere, the chance of visibility increasing with proximity to the north magnetic pole, which is currently in the arctic islands of northern Canada. Aurorae seen near the magnetic pole may be high overhead, but from further away, they illuminate the northern horizon as a greenish glow or sometimes a faint red, as if the sun was rising from an unusual direction. The aurora borealis most often occurs from September to October and from March to April. The Cree call this phenomenon the Dance of the Spirits. Its southern counterpart, the aurora australis/southern polar lights, has similar properties, but is only visible from high southern latitudes in Antarctica, South America or Australasia. Australis is the Latin word for "of the South". The northern lights have had a number of names through history. Benjamin Franklin first brought attention to the "mystery of the Northern Lights." He theorized the shifting lights to a concentration of electrical charges in the polar regions intensified by the snow and other moisture.

Folklore abounds with explanations of the origins of the spellbinding celestial lights. In Finnish they are called "revontulet", which means "fox fires" a name derived from an ancient fable of the arctic fox starting fires fire or spraying up snow with its brush-like tail. No matter that in English "foxfire" is a luminescent glow emitted by certain types of fungi growing on rotten wood. The true story is that the sun is the father of the auroras. The sun gives off high-energy charged particles (also called ions) that travel out into space at speeds of 300 to 1200 kilometres per second. A cloud of such particles is called a plasma. The stream of plasma coming from the sun is known as the solar wind. As the solar wind interacts with the edge of the earth's magnetic field, some of the particles are trapped by it and they follow the lines of magnetic force down into the ionosphere, the section of the earth's atmosphere that extends from about 60 to 600 kilometres above the earth's surface. When the particles collide with the gases in the ionosphere they start to glow, producing the spectacle that we know as the auroras, northern and southern. The array of colours consists of red, green, blue and violet. The Northern Lights are constantly in motion because of the changing interaction between the solar wind and the earth's magnetic field. The solar wind commonly generates up to 1000,000 megawatts of electricity in an auroral display and this can cause interference with power lines, radio and television broadcasts and satellite communications. By studying the auroras, scientists can learn more about the solar wind, how it affects the earth's atmosphere and how the energy of the auroras might be exploited for useful purposes.

An important centre for this type of geophysical study is located in Sodankylä, a small community in the heart of Finnish Lapland, at latitude 67.4 degrees north. It is an excellent location for probing the secrets of the earth's geomagnetic field. It was here that the Finnish Academy of Science and Letters established a geophysical observatory in 1913. Today, the Sodankylä Geophysical Observatory (SGO) is run by the University of Oulu. In addition to research the observatory performs routine geophysical measurements at its different stations. They produce ionospheric, geomagnetic and auroral data as well as seismic, cosmic ray data from Finland. The observatory and its associated research units nearby form a scientific community devoted to work that has global significance. There are high hopes that the brainwork of the scientists will also have beneficial effects on the local economy in this part of Lapland. The idea is that the findings of scientific research can be used to attract high-tech firms to the area, generating jobs and stimulating commercial activity. Already tourists can visit the privately operated "revontulikota", an auroral observatory and planetarium built in the shape of the traditional Lapp dwelling that is known as a "kota".


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