Wednesday, March 8, 2006

Solar Rivers of Plasma

The Solar and Heliospheric Observatory "uses sound waves in the sun's interior to reveal the details of its structure, much as a doctor uses ultrasound to get images of internal organs." The solar cycle is "powered by massive rivers of electromagnetic plasma flowing near the sun's surface from its equator to the pole and back again.

"The flow is like a massive conveyor belt, carrying large quantities of plasma—as well as isolated magnetic fields, or eddies—from the equator to the pole and back over a 22-year period, about twice the 11-year period of sunspot cycles."

"NASA's solar observatory found that the river of plasma flows poleward near the sun's surface, then dives about 125,000 miles toward the center of the sun before surfacing again at the equator, creating a massive loop.

"But the loop becomes distorted because the sun's equator and poles spin at different speeds. The fast spin at the equator tugs the plasma sideways, putting massive kinks into the loop. That injects energy and causes magnetic eddies to break through the surface, forming sunspots [about 25 to 30 degrees north of the equator]."

"The magnetic eddies that break through the surface release enormous amounts of energy, sending sheets of ionized particles and ultraviolet radiation toward Earth. Heat from the ultraviolet emissions causes the Earth's atmosphere to balloon slightly, increasing the drag on satellites in low-Earth orbit, including the International Space Station."

"Forecasting the strength of sunspots is important to satellite operators and other businesses, said Joseph Kunches of the National Oceanic and Atmospheric Administration's Space Environment Center in Boulder. Until now, such forecasts could be made only by extrapolating from past events, and those forecasts have not been very accurate.

"Dikpati and her colleagues used characteristics of one sunspot cycle to predict the next. Looking backward over records from the last 12 sunspot cycles, she said, the team has been able to predict the timing and magnitude of each successive cycle with 98% accuracy.

"They predict that the next sunspot cycle, called cycle 24, will begin in late 2007 or early 2008 and will produce sunspots across an area slightly larger than 2.5% of the sun's surface. [50% stronger than the last cycle] The cycle is likely to reach its peak about 2012." ...

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