Craft confirms solar-wind theory

Data from the Japanese Hinode spacecraft have confirmed that a set of long-theorized magnetic waves help power the solar wind that drives charged particles to the frigid boundary of the solar system.

Called Alfven waves in honor of the Swedish scientist who proposed their existence 60 years ago, they play an important role in accelerating the solar wind to speeds of around 2 million m.p.h., according to results published today in the journal Science.

"Until now, Alfven waves have been impossible to observe because of limited resolution of available instruments," said Alexei Pevtsov, a Hinode scientist at NASA in Washington. "With the help of Hinode, we are now able to see direct evidence of Alfven waves."

Hinode was launched in September 2006, the latest in a string of spacecraft trying to unravel long-standing solar mysteries, such as the origin of the sun's huge magnetic field, and the explanation behind the fact that the sun's atmosphere - or corona - is nearly a million degrees hotter than the surface.

In many ways, scientists say, the solar wind behaves like a wind blowing on Earth. Instead of leaves and tree branches flopping around, the solar wind propels a stream of electrically charged gas away from the sun in all directions.

The solar wind is part of a solar weather machine that generates sunspots, flares and big space storms called coronal mass ejections, which can knock power grids on Earth out of service.

As civilization has grown more dependent on technology, scientists have come to realize that understanding how the sun works is more than a matter of curiosity. Lives can depend on being able to predict major solar events.