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A coronal mass ejection in October 2003 shows up as a bright expanding ring around the sun. The inner white ring indicates the position of the sun's disc.
Great balls of fire
When the sun hurls flaming magnetic missiles at Earth, twin spacecraft carrying University-built instruments will sound the warning
By Deane Morrison
Oct. 24, 2006
In outer space as on Earth, real estate is all location, location, location.
That's particularly true for the twin spacecraft of NASA's STEREO mission, which will be positioned far apart in space to give the first binocular, or 3-D, view of the sun. On board are University-designed and built instruments to search for clues to how these explosions--the most powerful in the solar system--happen.
Launched the evening of Oct. 25, 2006, STEREO aims to learn more about the causes of spectacular eruptions of hot, magnetic bubbles of gas thrown off by the sun and how to identify those that are headed toward Earth, where they can disrupt power grids and communications. Seismology of the sun Known as CMEs (coronal mass ejections), the solar castoffs are an object of intense scientific interest. Through their experiment, called S/WAVES (STEREO Waves), University physicist Keith Goetz and colleagues at the University, the Paris Observatory and the University of California, Berkeley, will study radio waves and other signals tied to CMEs. Just as seismologists monitor ground tremors in hopes of identifying patterns that predict an imminent earthquake, the researchers want to find a pattern of solar activity that signals a CME is brewing. "It's all to understand and predict how the sun works," says Goetz, the project manager for S/WAVES. "We want to be able to look at the surface of the sun and say, for example, 'There's going to be an eruption--right there, in that spot.'" CMEs owe their capacity for mischief to electrically charged particles and magnetic fields embedded within them. Any doubt about their destructive potential was erased in March 1989, when the sun unleashed a CME that hit Earth's magnetic field and knocked out power to six million Quebec residents. The same electrical storm startled Minnesotans who turned on their radios only to find themselves eavesdropping on transmissions from the California Highway Patrol.
"STEREO is world class," Goetz says. "It's cool to create a sophisticated scientific instrument to fly in space."CMEs can also shut down satellites and send astronauts in orbit running for the shelter of their radiation shields.
Here comes the sun
>CMEs explode from the sun's corona, the wispy thin but sizzling--two million degrees F--outermost layer of the solar atmosphere.
>The sun has no solid surface, just layers of atmosphere that extend beyond Earth. Our planet is in the outer, cooler part of the corona.
>Packing the punch of a billion megaton bombs, a typical CME hurls a billion tons of the corona through space at up to 2.5 million miles per hour.
>CMEs follow the 11-year solar cycle, surging and ebbing in roughly the same rhythm as sunspots. About five CMEs per day are normal at the peak of solar activity, about one every other day when solar activity is minimal.
>The sun's energy varies no more than one-tenth of one percent over a decade.
>CMEs can cause outstanding displays of northern lights.
>According to the leading theory of CME formation, the eruptions are like the release of a balloon that strains at its guy wires--magnetic lines of force--until they snap.
>The sunbeams you saw today began in the sun's center hundreds of thousands of years ago.