March 25, 2009

U.K. scientists solve solar puzzle

U.K. scientists say they have solved one of the most puzzling features of the sun: why its outside atmosphere is hotter than its inner photosphere.

Researchers from Belfast's Queen's University and Britain's University of Sheffield said the surface of the sun, known as the photosphere, reaches temperatures of 5,000 degrees Celsius, while its outer atmosphere, known as the corona, can reach temperatures of more than 1 million degrees Celsius.

The scientists discovered evidence for the existence of a new kind of plasma oscillation called Alfven waves, which transport energy to heat the sun's corona. The phenomenon was first proposed by Hannes Alfven in 1942, but despite winning a Nobel Prize, hard evidence for the wave had not been found until now.

The team used the Swedish Solar Telescope to detect, for the first time, Alfven waves in the sun's lower atmosphere.

Queen's University scientist Daivd Jess, who led the research, said Alfven waves are invisible to the naked eye.

Only by examining the motions of structures and their corresponding velocities in the sun's turbulent atmosphere could we find, for the first time, the presence of these elusive Alfven waves, he said.

The study is detailed in the journal Science.