Giant "Space Tornadoes" Spark Auroras on Earth

Kate Ravilious
for National Geographic News
April 24, 2009

Even Dorothy would struggle to survive a "space tornado."

Whirling at more than a million miles per hour, these invisible, funnel-shaped solar windstorms carry electrical currents of more than a hundred thousand amps—roughly ten times that of an average lightning strike—scientists announced Thursday.

And they're huge: up to 44,000 miles (70,000 kilometers) long and wide enough to envelop Earth.

Led by the University of California astrophysicist Andreas Keiling, scientists have made the most detailed measurements yet of the space tornadoes, also known as substorm current wedges.

Their results shed light on how space tornadoes help spark auroras, also known as the southern or northern lights—the glowing colors that light up the night in polar regions.

(Related: "Aurora 'Power Surges' Triggered by Magnetic Explosions.")

The findings were made as part of the NASA's THEMIS (Time History of Events and Macroscale Interactions during Substorms) mission. THEMIS links 5 spacecraft and 20 ground observatories to measure how solar winds (charged particles from the sun) interact with Earth's magnetic field.

(Related: "Earth Atmosphere 'Breathes,' Thanks to Solar Winds").

"It is the first time that measurements from ground-based instruments and spacecraft have been combined in this way, and it gives us the most detailed picture yet" about the way our magnetic field responds to solar wind, said Timothy Horbury, a space physicist at Imperial College London, who wasn't involved in the study.

Spinning Up Auroras

As well as revealing the vast size and speed of these rotating plasmas of ionized gas, the team has pinpointed how space tornadoes kick-start the auroras we see on Earth.

"The tornado appears to ignite the aurora," said study leader Keiling, who presented the findings at a European Geosciences Union meeting in Vienna, Austria.

Continued on Next Page >>


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