In a first, physicists re-created the sun’s spiraling solar wind in a lab

Some of the sun’s fundamental physics have been re-created with plasma inside a vacuum chamber

Big Red Ball

SUN IN A BALL  This view shows the inside of the Big Red Ball, a 3-meter-wide aluminum sphere at the University of Wisconsin–Madison that can mimic properties of the sun. Carefully applied magnets and electric currents make the plasma spin and send out streams of charged particles, like the solar wind. 

Univ. of Wisconsin-Madison 

Physicists have created mini gusts of solar wind in the lab, with hopes that the charged particle streams can help to resolve some mysteries about our nearest star.

“We’re not re-creating the sun, because that’s impossible,” says plasma physicist Ethan Peterson of the University of Wisconsin–Madison, who reports the new work July 29 in Nature Physics. “But we’re re-creating some of the fundamental physics that happens near the sun.”

The sun spews a constant stream of charged particles, called the solar wind, out into space — though scientists aren’t sure exactly how (SN Online: 8/18/17). As the sun rotates, its magnetic field twists the wind into a helical shape called the Parker spiral, named after solar physicist Eugene Parker, who predicted the existence of the solar wind in 1958.

NASA last year launched its Parker Solar Probe to directly investigate the source of the solar wind (SN: 7/21/18, p. 12). But Peterson and colleagues found a way to mimic the Parker spiral much closer to home. 

The team used a 3-meter-wide aluminum vacuum chamber called the Big Red Ball at the Wisconsin Plasma Physics Laboratory to confine a ball of plasma heated to 100,000° Celsius. A magnet in the center of the ball mimics the sun’s magnetic field, and carefully applied electric currents send the plasma spinning and a wind streaming.

There are some unavoidable differences between the Big Red Ball and the sun, including size, gravity and temperature. Even so, the wind organized itself into a clear Parker spiral, as expected. The wind also occasionally ejected little blobs of plasma, each about 10 centimeters across. The sun ejects similar blobs, called plasmoids, but no one is sure why. The Big Red Ball could help provide an answer, Peterson says.

BALLERINA SKIRT The Parker spiral, which has also been described as a “ballerina skirt,” is the shape that the solar wind takes on as the sun rotates, twisting the wind into a helix as seen in a NASA simulation. Scientists mimicked this spiral in plasma in the lab. This video shows a smaller Parker spiral appearing in a ball of hot, spinning plasma inside a vacuum chamber. The bright spiraling structures follow the plasma’s magnetic field.

Lisa Grossman is the astronomy writer. She has a degree in astronomy from Cornell University and a graduate certificate in science writing from University of California, Santa Cruz. She lives near Boston.

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