Scientists at NASA'S Solar Dynamics Observatory have captured brilliant images of the iconic surfer's wave rolling through the atmosphere of the sun. This finding could provide clues on how energy moves through the sun's atmosphere called the corona.
It could provide valuable answers about the enduring mystery of why the corona is thousands of times hotter than originally expected.
The study will be facilitated by the fact that scientists are already aware of how these kinds of waves triggered by Kelvin-Helmholtz instability disperse energy in the water.
"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. People have suggested that waves like this might cause turbulence which cause heating, but now we have direct evidence of Kelvin-Helmholtz waves," states solar physicist Leon Ofman of NASA's Goddard Space Flight Center, Greenbelt, Md. and Catholic University, Washington.
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. As they flow past each other, slight ripples can be quickly amplified into the giant waves loved by surfers.
In the case of the solar atmosphere, which is made of a very hot and electrically charged gas called 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.
The difference in flow speeds and densities across this boundary sparks the instability that builds into the waves.
Surfer Waves and Sun
The fact that surfer waves exist in the sun is not a matter of surprise at all as they are spotted in many places in nature. This includes clouds on Earth and between the bands of Saturn.
However, Ofman states that despite the fact that Kelvin-Helmholtz instabilities have been spotted in other places, there was no guarantee they'd be spotted in the sun's corona, which is permeated with magnetic fields.
"I wasn't sure that this instability could evolve on the sun, since magnetic fields can have a stabilizing effect," he states. "Now we know that this instability can appear even though the solar plasma is magnetized."
Scientists believe that the friction created by turbulence, the simple rolling of material over and around itself could help add heating energy to the corona. The analogy is the way froth at the top of a surfing wave provides friction that will heat up the wave.