May 27, 2008 -- A fiery tornado towering more than 10,000 kilometers has been spotted twirling on the surface of the sun and firing white-hot charged particles into interplanetary space, say solar scientists.
The short-lived plasma twister of April 9, 2008, is leading to new insights about how some high-speed particles -- a particularly dangerous kind of heavy solar radiation for satellites and astronauts -- get catapulted towards Earth.
"What we see is that the twist is a key element," said Etienne Pariat, a solar scientist at George Mason University in Virginia.
The twist acts like a spring to push material out of the sun, he explained at a May 27 press briefing at the American Geophysical Union Joint Assembly in Fort Lauderdale, Fla.
The coiled eruption on the sun was one of three or four that happen every hour, though until now they were very hard to see and make sense of, explained Edward DeLuca, an astrophysicist at the Harvard-Smithsonian Center for Astrophysics.
The trick to the April 9 twister is that it was caught happening while the bright surface flare was just over the sun's horizon, and so out of view. That allowed the less bright parts of what was going on to become visible.
"It's a beautiful view of the process," said DeLuca.
By seeing it edge-on, it doesn't blind the telescopes on the X-Ray Telescope aboard the solar-observing Hinode satellite, he explained. "When the flare is behind the disk it's easier to see the flare structure."
Another key to confirming the tower of twisting plasma was the additional observations made by the two identical STEREO solar satellites which are a couple of million miles apart. The double images from different vantage points allowed scientists to literally untangle the lines of plasma and verify that this was, indeed, a tornado-like feature.
Before the STEREO satellites went into operation in 2006 solar scientists had no depth perception when they looked at the sun. So even though twisting features were seen, they were impossible to confirm.
"The situation here was dramatically improved when the information from STEREO became available," said Spiros Patsourakos, also of George Mason University.
With the new observations Pariat and Patsourakos were able to compare the real solar twisters to structures they have generated in computer simulations. The nice match they have found in this case means they are beginning to get a handle on how the sun makes these flares and eruptions. That in turn ought to help in the forecasting of space weather around Earth -- which is entirely ruled by the sun.
Storms of high-speed charged particles from the sun can create auroras, interfere with high latitude radio transmissions, create global electrical problems and damage satellites.
Related Links:
Larry O'Hanlon's blog: Earth Impacts
Discovery News blog: Free Space
Harvard-Smithsonian Center for Astrophysics
American Geophysical Union Joint Assembly
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