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THEMIS Satellites Discover What Triggers Northern Lights Eruptions
Researchers have discovered that an explosion of magnetic energy a third of the way to the moon powers substorms, sudden brightenings and rapid movements of the aurora borealis, called the Northern Lights.The culprit turns out to be magnetic reconnection, a common process that occurs throughout the universe when stressed magnetic field lines suddenly "snap" to a new shape, like a rubber band that's been stretched too far. "We discovered what makes the Northern Lights dance," said Dr. Vassilis Angelopoulos of the University of California, Los Angeles. Angelopoulos is the principal investigator for the THEMIS mission. Substorms produce dynamic changes in the auroral displays seen near Earth's northern and southern magnetic poles, causing a burst of light and movement in the Northern and Southern Lights. These changes transform auroral displays into auroral eruptions. Substorms often accompany intense space storms that can disrupt radio communications and global positioning system signals and cause power outages. Solving the mystery of where, when, and how substorms occur will allow scientists to construct more realistic substorm models and better predict a magnetic storm's intensity and effects. "As they capture and store energy from the solar wind, the Earth's magnetic field lines stretch far out into space. Magnetic reconnection releases the energy stored within these stretched magnetic field lines, flinging charged particles back toward the Earth's atmosphere," said David Sibeck, THEMIS project scientist at NASA's Goddard Space Flight Center in Greenbelt, Md. "They create halos of shimmering aurora circling the northern and southern poles." Posted by: 3dc 2008-07-26 |
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