Science of predicting space weather making strides

Web posted at: 10:17 AM EST (1517 GMT), January 3, 2000

SAN FRANCISCO (AP) -- As the sun reaches the peak of its 11-year cycle of activity this year, scientists say they are closer to understanding the process and more able to predict accurately the severity of solar storms.

Space weather forecasts are becoming important as more people and satellites are launched into space, and the world increasingly depends on sensitive electronics that can be fried by particles and radiation emitted by the sun.

Though researchers for years have noticed solar activity increases every 11 years or so, they have been unable to accurately predict the severity of the eruptions. The current cycle is expected to peak sometime in 2000.

"One funny thing about predicting solar activity is some people actually expect you to get it right," said David Hathaway, a researcher at NASA's Marshall Space Flight Center. "We've had a checkered past in terms of making predictions."

For nearly 150 years, scientists have observed that the dark blemishes on the solar surface known as sunspots pop up with much more frequency every 11 years. More recently, the spots have been associated with increased sun eruptions.

Sunspots and solar activity are the result of the star's magnetic field lines twisting and tangling as the sun rotates. Unlike the solid Earth, the gas that makes up the sun rotates at different speeds at different latitudes.

The sun magnetically unwinds by spewing out millions of tons of particles and gasses into space, producing a coronal mass ejection or solar storm, according to the most accepted theory.

Hathaway presented a study December 16 at the fall meeting of the American Geophysical Union examining several methods of prediction and compared their forecasts of previous cycles. Three forecast techniques proved reliable, he said.

All three used the Earth's magnetic fluctuations to predict as much as six or seven years in advance the intensity of the solar cycle. Previously, the most reliable estimates could be made only after the period of high activity began.

"There's something that's happening on the sun about the time of the solar minimum that is telling us ahead of time what the next cycle is going to be like," Hathaway said.

It appears the activity in 2000 will be slightly more intense than average, he said.

Earth is protected from the radiation, particles and gasses by its atmosphere and own magnetism. For billions of years, the only visible effect has been an increase in the spectacular northern and southern lights near the planet's poles.

The electronics inside satellites are sensitive to the energized particles -- as are the cells of astronauts who venture beyond the Earth's protective fields. On Earth, power grids also are susceptible to power surges from the solar events. And radio communications can be disrupted during intense storms.

"What's kind of new about this solar cycle as opposed to other solar cycles is how we use space," said Victor Pizzo of the U.S. Space Environment Center. "Right now we have a whole slew of satellites in orbit for communications and all kinds of stuff."

Because the eruptions occur so far away, scientists usually have several days' warning before the bulk of material blows past Earth.