SUN MAY ADD TO DISCOMFORT OF Y2K BUG BITES.

Byline: Paul Recer Associated Press 

As if potential Year 2000 computer problems are not enough, stormy weather predicted on the sun early next year also could torment Earth's technology.

That could mean celebrating the new millennium in the dark, with a dead cellular phone. Ships and planes relying on satellites for navigation might have trouble. Even spacewalking astronauts are at risk of problems.

Using new techniques, researchers are forecasting the sun is going to enter the most violent and disruptive part of its 11-year cycle. The worst is expected to begin in January, also when computers around the world will struggle to cope with possible problems caused by the Y2K bug.

Severe solar storms erupting with massive bursts of magnetic energy and radiation are expected to continue at their peak until April.

Coronal mass ejections, which are solar explosions that can equal one million 100-megaton bombs, and solar flares send waves of energy toward Earth.

They can cause power blackouts, block some radio communications and trigger phantom commands capable of sending satellites spinning out of their proper orbits.

There could be trouble for cellular telephones, global positioning signals and spacewalking astronauts, experts said Monday at a national meeting of the American Astronomical Society.

There were two pieces of good news: The disruptive stage of the solar cycle is not expected to be as severe as some in the past, and for the first time there could be some warning. A government satellite will detect bursts of solar energy and send about an hour's notice, said JoAnn Joselyn of the National Oceanic and Atmospheric Administration.

That warning, posted on the Internet and relayed through a special system, will give power companies time to align circuits to minimize or avoid damage from electrical surges, she said. Satellite operators can power down equipment or prepare to send corrective signals to their spacecraft.

Scientists have plotted 23 solar cycles, using historic and modern measurements. But this one has the greatest potential for disrupting activities on Earth because much of the vulnerable communications technology is new since the last period of maximum natural violence on the sun, Joselyn said.

``The explosion in technology is intersecting with an extremely disturbed space environment,'' Joselyn said. ``There is much higher risk now because we depend more on technology that is vulnerable.''

Joselyn said energy bursts from the sun can cause an electrical charge to build up on the surface of satellites, triggering phantom signals.

In an earlier solar cycle, she said, small rocket thrusters on one satellite suddenly started firing, sending a spacecraft out of position. Control of another satellite was lost when its gyroscopes were disrupted.

Joselyn said cellular telephones are vulnerable because they might use the ionosphere, the region of electrically charged gases in the upper atmosphere, to send radio signals, and bursts from the sun can disturb the ionosphere. Some cellular phone systems depend on satellites that are at risk, too.

Solar energy eruptions can cause warm air to surge up from Earth. That can drag some satellites to lower orbits, forcing satellite operators to use rocket fuel to reposition the spacecraft.

Worldwide ships and airplanes rely heavily for navigation on the Global Position Satellite System, which uses a fleet of satellites that can be affected by the sun, said Joselyn.

``I am worried about the GPS system more than anything else,'' she said. ``We're starting to land airplanes with that system now.''

Electromagnetic energy from the sun can send huge waves of electrical energy surging along power lines, shorting circuits and burning out equipment. In 1989, a solar storm caused a blackout throughout Quebec, and a transformer station in Salem, N.J., melted and caught fire, causing a regional outage there.

Astronauts generally are safe inside the shuttle or the International Space Station, but future missions to the moon or to Mars could be troubled by solar radiation bursts.

``On the moon, they could get enough radiation to be lethal,'' said Joselyn. ``If we fly to Mars, we'll have to consider the hazardous radiation from the sun.''