14 DAY TRIAL // In two new studies published on November 12, at the Hinode 7 Science Meeting in Japan, researchers from the Columbia University provide potential explanations for why the solar atmosphere is hotter than the star's surface. This mystery has baffled astronomers for decades, but clear explanations have thus far eluded them.
Scientists calculated a long time ago that the corona surrounding the Sun – its atmosphere – has a temperature of more than one million degrees Kelvin. At the same time, the actual surface of the star only reaches temperatures of about 6,000 degrees. Further down, the nuclear fusion-sustaining core reaches temperature levels in excess of 15 million degrees.
The reason why such massive variations in temperature exist between these different layers of the Sun has thus far not been explained comprehensively. The two recent studies may provide some new insight into the processes that underlie these differences.
Using funds from the US National Science Foundation (NSF), CU investigators determined that magnetic waves known as Alfven waves may be responsible for these wild temperature swings. The discovery was made using data from the Japanese Hinode satellite and its Extreme Ultraviolet Imaging Spectrometer instrument.
The research team, led by astronomers Michael Hahn and Daniel Wolf Savin, analyzed a hole Hinode observed in a polar section of the solar corona. Scientists found that magnetic field lines within the Sun pulsate, thus transferring energy from within the solar core to the corona.
“This is a fundamentally important finding. This issue is the holy grail of solar physics. If this allows us to better understand the mechanics, then it has tremendous consequences,” says the director of the solar terrestrial research program at the NSF, Ilia Roussev.
“This is the big, unanswered question in solar physics, and nearly everyone in the field is somehow working on trying to solve it. We really had no idea where the research would lead us, but we were hoping to at least be able to add another piece to the puzzle. We did not expect it to be such a big piece,” adds Savin.
Now that solar physicists know what to look for, additional data on how magnetic field lines may be underlying temperature variations within the Sun may soon become available.