April 2, 2008 -- The solar wind paints Earth's skies with auroras and pushes solar sails through space, but just how the streams of electrically charged particles flow out of the sun has been a mystery until now.
"It has been debated for many years," said Louise Harra, a University College London researcher who on Wednesday unveiled the sun's secret.
Like most phenomena associated with stars, the process is violent. An international team of scientists discovered that pockets of hot gases on the sun's surface, which pool around bright knots of magnetic activity, spurt out into space when the sun's snarling, snaking magnetic fields collide.
At the Royal Astronomical Society meeting, Harra planned to show images from the orbiting Hinode spacecraft showing magnetic fields linking two bright spots on the sun that were nearly 500,000 kilometers, or 311,000 miles, apart -- a distance equivalent to 40 Earths placed side by side.
When the magnetic fields smashed into each other, charged gases flew out in all directions, forming the solar wind.
"It is fantastic to finally be able to pinpoint the source," Harra said, adding that the next step is to figure out how the wind is transported through the solar system.
The solar wind permeates the solar system, actually defining its shape and scope, as it blasts along at 125 miles per second on the slow days.
During snappier binges, strong gusts blasting into Earth's magnetic bubble can have a myriad of ramifications from the beautiful and benign aurora above Earth's poles to the shutdown of power and communications systems on the planet.
At the same meeting, astronomers also discussed the forces behind volcanic-type explosions of gas from the sun's atmosphere. These so-called fountains are places of increased pressure at the base of the sun's magnetic fields, said Michelle Murray, also from University College London.
As the magnetic fields rearrange themselves, the pressure periodically tails off, allowing the gases to fall back toward the sun's surface. Computer simulations based on Hinode data show that when a new section of magnetic field pushes through the solar surface, it generates a continual cycle of fountains.
"New magnetic fields are constantly emerging across the whole of the solar surface, so our results can explain a whole multitude of fountains that have been observed," Murray said.
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