Over the Arctic, Auroras Collide

Two curtains of light known as the aurora borealis have been caught in a collision by NASA cameras deployed around the Arctic, creating a spectacular explosion of light.

These auroral collisions, which had never been seen before or known to exist, were described for the first time here today at the annual meeting of the American Geophysical Union.

The unexpected collisions were spotted by a network of all-sky imagers set up by NASA and the Canadian Space Agency for the THEMIS (Time History of Events and Macroscale Interactions during Substorms) mission. Their aim was to find out why some auroras occasionally exploded in light, an event known as a substorm.

Auroras are created when particles in the solar wind rushing off the sun interact with Earth's magnetic fields at its poles.

Earlier this year, UCLA scientist Toshi Nishimura assembled continent-wide scale movies from the individual cameras. The first movie he made showed a pair of auroras crashing together in December 2007.

"Our jaws dropped when we saw the movies for the first time," said space scientist Lary Lyons of UCLA, a member of the team that made the discovery. "These outbursts are telling us something very fundamental about the nature of auroras."

The collisions occur on such a vast scale that someone looking up from a single vantage point on Earth's surface wouldn't notice them. But the cameras, which look over a much wider distance, can see the whole picture.

After the evidence from the first movie, the team looked for more such collisions and "our excitement mounted as we became convinced that the collisions were happening over and over," Lyons said.

The scientists think that the spectacular light explosions are a sign of dramatic goings-on in the space around the Earth, or its "plasma tail." ...

via Over the Arctic, Auroras Collide - Yahoo! News.