Explosive bursts normally seen only on the surface of the sun can now be captured in a 13-foot-long tube using lab-created plasmas and bursts of laser light.

Physicists have created a scaled-down model of solar eruptions called coronal mass ejections, which can wreak havoc on satellites and create beautiful northern-light displays on Earth. The new experiments suggest these eruptions are set off when gushes of charged particles flow into twisted loops of magnetic field that extend from the sun's upper atmosphere.

"You can do things in the lab that are absolutely impossible to do in space," said plasma physicist Walter Gekelman of the University of California, Los Angeles. Gekelman and UCLA physicist Shreekrishna Tripathi created miniature versions of enormous loops of solar matter called arched magnetic flux ropes. Their results are described in the Aug. 13 issue of Physical Review Letters.

These twisted magnetic ropes -- also sometimes called coronal loops, prominences and filaments -- can sit comfortably on the sun's surface for hours or days, transporting energy and matter from the solar surface to the outer atmosphere. But eventually they explode, shooting tons of charged particles out into space like a slingshot. These loopy time bombs have been photographed by observatories like the Solar and Heliosespheric Observatory -- but how they form, and what makes them collapse, is still unknown.

"Astronomical observations give you pictures of things. It's hard to deduce what's going on inside of it," said plasma physicist Steven Spangler of the University of Iowa, who was not involved in the new work. "So you'd really like to have a lab experiment to give you a scaled down version and bigger insights."

Some theoretical models have suggested the eruptions are triggered by jets of plasma, or gas that is so hot that all the electrons have been stripped away from their parent atoms. These plasma jets are injected directly from the sun into the roots of the magnetic arcs.

To test this idea, the team of physicists used a cylindrical vacuum chamber about 13 feet long and 3 feet wide to hold a background plasma. Earlier experiments used a spark to create a plasma arc that simulated the solar loops, but without a background plasma, those loops fell apart too quickly to be realistic.

"Those conditions are very very different than in a real flux rope," he said. "In the sun, there's plasma everywhere, not just in the flux rope."

Gekelman and Tripathi used two electromagnets to create an arched magnetic field, which produced a second plasma, analogous to the solar flux rope. They then fired two identical laser beams at carbon rods placed just behind the electromagnets, which shot two jets of carbon plasma directly into the ends of the flux rope.

These plasma jets created a destabilizing kink in the flux rope, making it erupt and send waves of energy rippling through the background plasma.

"They're completely stable until we eject flow into them," Gekelman said. "Then they go nuts."

The experiment doesn't absolutely prove plasma jets are responsible for coronal mass ejections, but "it's a hint and an indicator and should stimulate additional research," Spangler said. "We're beginning to get some hints into what are the crucial ingredients."

Image: 1) ESA/SOHO 2) S. Tripathi and W. Gekelman

See Also:

• 3-D Solar Tsunami Video Shows the Extreme Waves Are Real
• Sun's Plasma Bursts Use Earth As “Magnetic Slingshot”
• Northern Lights' Source Found in Giant “Magnetic Ropes”
• Video: The Butterfly Effect on the Sun's Surface
• Video: Sun Puts on a Spectacular Eruption Show

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