NASA's STEREO shows where solar wind comes from

"Now we have a global picture of solar wind evolution," said NASA researcher Nicholeen Viall.

By Brooks Hays

BOULDER, Colo., Sept. 1 (UPI) -- Thanks to NASA's Solar Terrestrial Relations Observatory -- their STEREO -- scientists now have a much clearer idea of where and how solar wind forms.

What scientists didn't exactly understand, until now, was how structured and straight solar rays become the twisting and turbulent winds that travel outward through the solar system.


Solar rays don't swirl as they protrude from the corona, the sun's upper atmosphere, but follow straight lines.

At some point, they make the transition to solar wind. The new STEREO imagery has revealed that point as the outer edge of the corona, the outer bondary of the sun.

RELATED High-res imagery showcases solar flare in action

After using an algorithm to dim the appearance of gas, dust and polluting starlight in the new images, researchers were able to watch stellar rays break up and become solar wind in slow motion.

The moving images reveal the important role the sun's magnetic field plays in controlling the structure of its rays. As they near the sun's boundary, the rays turn from plasma to gas.

"As you go farther from the sun, the magnetic field strength drops faster than the pressure of the material does," Craig DeForest, solar physicist at the Southwest Research Institute, said in a news release. "Eventually, the material starts to act more like a gas, and less like a magnetically structured plasma."


Scientists have previously hypothesized that the sun's magnetic field dictates the appearance and behavior of its plasma rays, but now they have detailed evidence of the process.

Researchers hope the insights provided by the new imagery will improve their understanding of the large-scale physics that govern the sun and the rest of the solar system.

"Now we have a global picture of solar wind evolution," added Nicholeen Viall, solar scientist at NASA's Goddard Space Flight Center. "This is really going to change our understanding of how the space environment develops."

RELATED Study explains mysterious 'eclipse wind'

Researchers described the breakthrough images in this week in the Astrophysical Journal.

Latest Headlines