U.S. scientists identify what powers Northern Lights

Using a fleet of five NASA satellites, U.S. scientists have identified the mechanism that triggers substorms in space and leads to the explosive release of energy that causes the spectacular brightening of the aurora borealis, or the Northern Lights, NASA reported Thursday.

File photo of the Northern Lights.Using a fleet of five NASA satellites, U.S. scientists have identified the mechanism that triggers substorms in space and leads to the explosive release of energy that causes the spectacular brightening of the aurora borealis, or the Northern Lights, NASA reported Thursday.

For 30 years, there have been two competing theories to explain the spectacular Northern Lights dancing.

One is that the trigger happens about one-sixth of the distance to the moon, when charged ions and electrons implode toward Earth as the space currents are disrupted.

A second theory says the trigger is farther out, about one-third of the distance to the moon. When two magnetic field lines come close together due to the storage of energy from the sun, a critical limit is reached and the magnetic field lines reconnect, causing magnetic energy to be transformed into kinetic energy and heat.

"Our data show clearly and for the first time that magnetic reconnection is the trigger," said Vassilis Angelopoulos, the principal investigator of the five-satellite THEMIS project." Reconnection results in a slingshot acceleration of waves and plasma along magnetic field lines, lighting up the aurora underneath even before the near-Earth space has had a chance to respond."

Previous studies of the Earth's magnetosphere and space weather have been unable to pinpoint the origin of substorms, which are large magnetic disturbances.

"We need to understand this environment and eventually be able to predict when these large energy releases will happen so astronauts can go inside their spacecraft and we can turn off critical systems on satellites so they will not be damaged," Angelopoulos said. "This has been exceedingly difficult in the past, because previous missions, which measured the plasma at one location, were unable to determine the origin of the large space storms."

THEMIS stands for Time History of Events and Macroscale Interactions during Substorms mission. Launched on Feb. 17, 2007, THEMIS is expected to observe approximately 30 substorms in its nominal lifetime.

North Pole could be ice-free this summer

Arctic sea ice could break apart completely at the North Pole this year, allowing ships to sail over the normally frozen top of the world.

The potential landmark thaw - the first time in human history the pole would be ice-free - is a stark sign of global warming, according to an article Friday on the web site of the The Independent, a London newspaper.

"Symbolically it is hugely important," said Mark Serreze of the US National Snow and Ice Data Center in Colorado. "There is supposed to be ice at the North Pole, not open water."

Last year, the fabled Northwest Passage opened as Arctic ice retreated more than ever before.

A picture taken 2007 shows a glacier seen from the Ice Fjord on the Norwegian Arctic archipelago of Svalbard. There could be a brief time this summer when there is no ice on the North Pole, a US scientist said Friday, blaming global warming that has melted the Arctic ice sheet over decades.

There is no land at the North Pole, but as long as anyone has looked, it has remained a giant block of ice year-round. Scientists have been watching Arctic sea ice melt more and more each year. But each summer in recent years, the amount of ice has gotten thinner and thinner. Each winter's freeze, therefore, results in a thinner pack that, this summer, could melt altogether.

"The issue is that, for the first time that I am aware of, the North Pole is covered with extensive first-year ice," Serreze is quoted by The Independent. "I'd say it's even-odds whether the North Pole melts out."

Russia and other countries, meanwhile, have been arguing over who has rights to the region's resources, including potential oil reserves.

Several studies in recent years have predicted that the North Pole could be ice-free within a few decades. Alarm has ratcheted up every summer as the ice gets thinner and thinner. In a study released June 10, scientist said the rapid meltoff in the Arctic could threaten permafrost in continental soil elsewhere above the Arctic circle in a warm version of the snowball effect.

Last summer saw a record melt of Arctic sea ice, which shrank to more than 30 percent below its average. Around the peak of the melt, in September, air temperatures over land in the western Arctic from August to October were more than 4 degrees Fahrenheit (2 degrees Celsius) above the 1978-2006 average.