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.

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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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