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Splendour in the sky How to watch Effects of Aurora Borealis Beliefs of indigenous people The Northern Lights in HistoryRelated sites
Splendour in the sky |
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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 1,000,000 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. |
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