SDO Catches Surf Waves on the Sun
Date- 24th March 11 Source- http://svs.gsfc.nasa.gov/vis/a010000/a010700/a010745/index.html 'Scientists have spotted the iconic surfer's wave rolling through the atmosphere of the sun. This makes for more than just a nice photo-op: the waves hold clues as to how energy moves through that atmosphere, known as the corona. Since scientists know how these kinds of waves -- initiated by a Kelvin-Helmholtz instability if you're being technical -- disperse energy in the water, they can use this information to better understand the corona. This in turn, may help solve an enduring mystery of why the corona is thousands of times hotter than originally expected. 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. In order to confirm this description, the team developed a computer model to see what takes place in the region. Their model showed that these conditions could indeed lead to giant surfing waves rolling through the corona. Seeing the big waves suggests they can cascade down to smaller forms of turbulence too. 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.'