Instabilities build up on one flank of clouds of material exploding from the sun. The instabilities may explain why coronal mass ejections bend and twist instead of following a straight path.
By John Roach
When clouds of material explode from the sun, instabilities appear to form and build up on one flank of the ejected material, new observations from NASA’s Solar Dynamics Observatory show. Because these instabilities are similar to those observed in Earth’s clouds and oceans, researchers have a new tool for predicting space weather.
The observations of the outbursts, called coronal mass ejections or CMEs, were made in the extreme ultraviolet at a temperature range previously unavailable — 11 million Kelvin, according to astrophysicists at the University of Warwick in Britain, who are studying the images made with the observatory’s Atmospheric Imaging Assembly.
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According to the team, the so-called Kelvin-Helmholtz (or KH) instabilities appear to roll up into growing whirls at boundaries between materials moving at different speeds. The difference in speed produces boundary instabilities.
The instabilities in the CMEs closely parallel instabilities seen in Earth’s atmosphere, and in waves on the surface of the seas. Scientists had predicted they occur within the solar system’s weather, but this is the first time the ripples have been directly observed in the sun’s corona.
The researchers studying the images are particularly intrigued by how the instabilities build up on one side of the CME — this may explain why CMEs appear to bend and twist instead of following a straight path from the surface of the sun. Further understanding the results could assist physicists trying to understand and predict space weather.
“If the instabilities form on just one flank, they may increase drag on one side of the CME causing it to move slower than the rest of the CME,” Claire Foullon, a researcher at the University of Warick, said in an image advisory.
A paper outlining the observations and detailed modeling on how they the phenomenon occurs appears in the Astrophysical Journal Letters.
More stories on coronal mass ejections:
* Here comes the sun storm * Solar shocker: Sun storms change directions * Photoblog: Double whammy on the sun * See a twister on the sun
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John Roach is a contributing writer for msnbc.com. Connect with the Cosmic Log community by hitting the “like” button on the Cosmic Log Facebook page or following msnbc.com’s science editor, Alan Boyle, on Twitter (@b0yle).