Dorothy's tornado was nothing compared to the giant swirls
of plasma that storm in outer space.
Space tornadoes are funnels of hot charged particles around
the Earth that flow at more than a million mph (1.6 million kph). As the ions
circle, they produce strong electrical currents that help create the gorgeous light show known as the
aurora.
New observations of these cosmic
storms by a suite of NASA spacecraft
called THEMIS (Time History of Events and Macroscale Interactions during
Substorms) help shed light on their inner workings. THEMIS found that space
tornadoes can produce electrical currents greater than 100,000 amperes (for
comparison, a 60-watt light bulb draws about half an ampere).
The tornadoes then channel this current of flowing electric
charge along twisted magnetic field lines into Earth's ionosphere to spark
bright and colorful auroras.
Andreas Keiling, a space physicist at the University of
California, Berkeley's Space Sciences Laboratory, presented THEMIS's findings
today at the general assembly of the European Geosciences Union in Vienna,
Austria.
The five space probes that make up THEMIS lifted off in
February 2007 on
a mission to study the origin of magnetic storms that power the aurora
(also known as the Northern and Southern Lights).
THEMIS measured the tornadoes while traveling through them
at about 40,000 miles above Earth. Ground telescopes watched simultaneously to
confirm the observations.
The intense currents don't pose any threat to humans, the
researchers said. But on the ground they can damage man-made communication devices,
such as power transformers.
A better understanding of all this is needed to improve
space storm forecasting and to predict what might happen to power grids.
Experts say the next period of maximum solar activity — due
around 2012 — could bring a level of storminess not seen in many decades. A recent report by the National Academy of Sciences
concluded that a major storm during the next peak could
cripple power grids and other communications systems, with effects leading
to a potential loss of governmental control of the situation.
Other members of the team include Karl-Heinz Glassmeier of
the Institute for Geophysics and Extraterrestrial Physics (IGEP, TU) in
Braunschweig, Germany, and Olaf Amm of the Finnish Meteorological Institute.
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