New theory for sun's ring of fire
Sound, not Johnny Cash, responsible
Scientists have proposed a new mechanism to explain the so-called ring of fire that is visible around the sun during a full solar eclipse.
Previously it was thought that the photosphere, the sun's visible surface, trapped the sound waves that bound around its interior. But the research (presented at the American Astronomical Society Meeting in Hawaii) reveals that they can escape into the ring of fire, or chromosphere as it is more formally known, and even into the corona.
The data suggests that sound waves escaping from the sun's interior create plumes of hot gas, which in turn power the ring of fire.
The chromosphere is a thin region of the sun's atmosphere that is orders of magnitude hotter than the solar surface. It is particularly important because it is largely responsible for the deep UV radiation that produces our ozone layer. It is also very strongly related to climate variability.
These results help explain why the region is so hot, the researchers say.
"The sun's interior vibrates with the peal of millions of bells, but the bells are all on the inside of the building. We have been able to show how the sound can escape the building and travel a long way using the magnetic field as a guide," explains Scott McIntosh, a researcher at Southwest Research Institute in Colorado.
Using observational data from several observatories - space and ground based - the team was able to construct a model showing how the trapped sound waves can leak out of the photosphere and into a magnetic "mould" that forms the chromosphere. The leaks appear to be linked to strong knots of magnetic field.
"The constantly evolving magnetic field above the solar surface acts like a doorman opening and closing the door for the waves that are constantly passing by," said Bart De Pontieu, a researcher at Lockheed Martin Solar and Astrophysics Lab.
The constantly changing magnetic field makes it possible for wave motions to pump much more energy into the chromosphere than had previously been thought, the scientists say. ®