Sun clouds explode with familiar ripple

U. WARWICK (UK) — Instabilities forming in clouds of material exploding from the Sun appear to have similarities to clouds in the Earth’s atmosphere.

Scientists believe that the findings, discovered during an examination of new images of coronal mass ejections (CME), could help understand and predict weather in our solar system.

The images are provided by the Atmospheric Imaging Assembly (AIA) experiment on NASA’s Solar Dynamics Observatory (SDO), that was launched last year and provides unprecedented views of the Sun in multiple temperatures.

The new SDO/AIA observations provided images of coronal mass ejections in the extreme ultraviolet at a temperature that was not possible to observe in previous instruments—11 million Kelvin.

Researchers spotted a familiar pattern of instability on one flank of an exploding cloud of solar material that closely paralleled instabilities seen in Earth’s clouds and waves on the surfaces of seas.

Details are reported in Astrophysical Journal Letters.

The Kelvin-Helmholtz (KH) instabilities appear to roll up into growing whirls at boundaries between things moving at different speeds, for instance the transition between air and water or cloud. The difference in speeds produces the boundary instabilities.

Similar conditions can occur when one looks at the magnetic environment of the path of these coronal mass ejections as they travel through the solar corona. The difference in speed and energies between the two creates the very similar KH instabilities observed in clouds.

While KH instabilities have been predicted or inferred from observations as happening within the solar system’s weather this is the first time they have been directly observed in the corona.

Researchers say what makes this observation even more interesting is that the instabilities appear to form and build on one flank of the CME, which may explain why the ejections appear to bend and twist as these instabilities build, and cause drag, on one side of the cloud.

“The fact that we now know that these KH instabilities in CMEs are so far only observable in the extreme ultraviolet, at a temperature of 11 million Kelvin, will also help us in modeling CME behavior,” says Claire Foullon the University of Warwick.

“This new observation may give us a novel insight into why these CMEs appear to both rotate, and be deflected away from following a simple straight path from the surface of the Sun.

“If the instabilities form on just one flank they may increase drag one side of the CME causing it to move slower than the rest of the CME.”

Scientists from Embry-Riddle Aeronautical University and the University of New Hampshire contributed to the research.

More news from University of Warwick: