August 18, 2014 - Small "nanoflares" erupting from the sun might be the key to unlocking a cosmic mystery, according to a new study.
Scientists have found that the sun's outer atmosphere, or corona, can reach temperatures 1,000 times higher than those at the surface of the star, but solar physicists previously had no explanation for why this temperature discrepancy is so great. Now, researchers think the relatively tiny flares may be the "smoking gun" that explains this mysterious cosmic occurrence.
The new study provides the first direct proof that nanoflares keep the sun's corona at a temperature of millions of degrees, far hotter than the sun's visible surface, which is about 6,000 degrees Kelvin (10,000 degrees Fahrenheit). [The Biggest Solar Flares of 2014: Photos]
"The nanoflare model has been around for a while," said Jeffrey Brosius, a solar physicist at NASA's Goddard Space Flight Center in Greenbelt, Maryland "With better instrumentation, we were hoping to find the evidence that was predicted by the model."
Nanoflares happen because of huge magnetic fields located throughout the sun's corona. These loops are anchored in the photosphere, the sun's visible surface, but move around due to turbulence in the photosphere. Sometimes the field lines cross, and they become twisted and tangled.
When this happens in the presence of plasma, current sheets form, and the "stress" builds until the magnetic field "breaks," releasing lots of energy very quickly. This kind of crossing of magnetic fields can happen thousands of times a second over the whole solar surface, and this transfers energy to the plasma in the corona. That energy transfer could explain the corona's extra heat.