Surf Waves Imaged in Sun's Atmosphere

A team of experts at the American space agency announce that one of their monitoring spacecraft was recently able to snap an interesting view of surf wave-like features developing in the solar atmosphere.

The group explains that these features traversing the corona may hold clues as to how exactly energy is transferred through this layer of the Sun. In turn, this might help solar physicists understand how the star operates in more detail than ever before.

At the same time, this line of investigation could finally answer the decades-old question of why the solar corona is many times hotter than the actual Sun, and considerably more so than theoreticians predicted in their computations.

The solar waves were discovered in images taken on April 8, 2010 by the Solar Dynamics Observatory (SDO) satellite, which NASA keeps pointed at the star at all times. The instrument is capable of providing round-the-clock monitoring capabilities.

“One of the biggest questions about the solar corona is the heating mechanism. The corona is a thousand times hotter than the Sun's visible surface, but what heats it up is not well-understood,” explains expert Leon Ofman.

“People have suggested that waves like this might cause turbulence which cause heating, but now we have direct evidence of Kelvin-Helmholtz waves,” he adds. The expert is a solar physicist at the NASA Goddard Space Flight Center (GSFC), in Greenbelt, Maryland.

He also holds an appointment at the Catholic University in Washington. The investigator worked with GSFC colleague Barbara Thompson in identifying and studying the solar waves SDO discovered.

Details of the work the two conducted was detailed in the May 19 online issue of the esteemed Astrophysical Journal Letters, and will also appear in the June 10 print issue of the publication.

“The waves we're seeing in these images are so small. They're only the size of the United States,” Thompson says laughing. She is a coauthor on the new paper, and also the deputy project scientist for the SDO mission.

“Kelvin-Helmholtz instabilities occur when two fluids of different densities or different speeds flow by each other. In the case of ocean waves, that's the dense water and the lighter air,” a NASA press release states.

“In the case of the solar atmosphere, which is made of […] plasma, the two flows come from an expanse of plasma erupting off the sun's surface as it passes by plasma that is not erupting,” it adds.

“The difference in flow speeds and densities across this boundary sparks the instability that builds into the waves,” the statement concludes.