Earth's Magnetic Field
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The earth acts like a bar magnet. Study of the magnetic field gives more clues about the earth's core including the recent discovery that part of the core may be rotating more rapidly than the outer part of the earth. The earth's relatively strong magnetic field is a consequence of its fast rotation rate and molten iron core. (From Liftoff to Space Exploration, MSFC, http://liftoff.msfc.nasa.gov/academy/space/mag_field.html) |
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When the wind of particles from the sun approaches the earth, they are deflected by the magnetic field. At low latitudes, (within 50 degrees of the equator) the particles get trapped in the Van Allen Belts, zones of intense radioactivity around the earth's midsection. At these latitudes, the magnetic field shields us from intense radioactivity during solar storms. (From Windows to the Universe, http://www.windows.ucar.edu/) |
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Above the north and south poles, the magnetic field has less effect and the particles can get low enough to interact with the atmosphere, where they create aurorae (northern or southern lights) visible from latitudes near the poles. Picture by Jan Curtis, http://www.geo.mtu.edu/weather/aurora/images/aurora/jan.curtis/ |
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Picture from the Space Shuttle Endeavour of the southern aurora. (From L. Frank and J. Sigworth, http://www-istp.gsfc.nasa.gov/istp/outreach/afromspace.html) |
For more about the magnetism of the earth, see http://www.agu.org/sci_soc/cowley.html