By Kathy Sawyer
Washington Post Staff Writer
Wednesday, March 10, 1999; Page A2

Scientists have discovered a way to predict the eruptions of powerful solar magnetic storms aimed at Earth, giving civilization extra time to protect its growing networks of communications, power and other electronic conveniences.

An international team of scientists yesterday reported their discovery that the appearance of a giant "S," etched in X-rays in the sun's blazing halo, is a "reliable indicator" that the site within days will launch a cloud of perhaps 10 billion tons of hot, electrically charged gas into space with the energy of a billion megatons of TNT.

Aside from the discovery's potential practical benefits, they said, the research also represents a significant advance in understanding the workings of the star that sustains life on Earth.

Several times a day, in all directions, the sun shoots one of these violent discharges from its outer halo, known as the corona. These coronal mass ejections (CMEs) are the largest, most violent explosions known on the sun's surface (or anywhere in the modern solar system), but have been observed only since the 1970s. Perhaps one or two dozen times a year, a significant burst is aimed toward Earth, traveling at between 1 million and 2 million miles per hour.

The ejected clouds take two to four days to cross the 93-million mile distance between the sun and Earth. A protective bubble created by Earth's own magnetic field shields the planet from most of the effects from ordinary solar storms. The impact depends on the quantity and velocity of the ejection and the character of the magnetic field it carries. A serious one can damage satellites, disrupt global communications and cause power blackouts like one that occurred in Canada's Quebec province 10 years ago this month, as the sun reached a peak of activity in its 11-year cycle. Another such peak is predicted for next year. [For more about the sun's workings and its impact on satellites and power systems, see today's Horizon section.]

With sufficient warning, satellite operators can turn off high voltages on their craft to prevent them from self-destructing when the overload hits, and utility companies can shut down some of the $10 million transformers in their power systems in anticipation of the impending surge of DC current, according to Gary Heckman, a senior forecaster at NOAA's Space Environment Center in Boulder, Colo.

Space weather forecasters generally try to monitor such storms as they leave the sun. But, he said, they can provide an accurate forecast of the impact only a half hour to an hour in advance of the storm's arrival at Earth. If the new findings produce much earlier forecasts, Heckman said, "that will be very valuable."

Images from the Japanese-U.S.-British satellite Yohkoh indicate that the same powerful magnetic forces that trigger the ejections first tend to form an "S" pattern (possibly a backward S, depending on the hemisphere) up to 100,000 miles long over the sun's surface. Each S is thought to be the exposed edge of a twisted, three-dimensional coil of magnetic field lines – a structure that resembles a gigantic slinky toy.

The telltale skywriting – which can only be observed from above Earth's interfering atmosphere – is emitted in X-ray wavelengths by charged particles trapped in the writhing field lines and glowing at temperatures ranging up to several million degrees.

The researchers, who discussed the discovery at a NASA briefing here, likened the significance of the S-shaped pattern to that of a "loaded gun" with a high probability of firing. "We've found that the S-shaped regions are the dangerous ones," said physicist Richard Canfield of Montana State University in Bozeman. "As soon as we can recognize that a region is S-shaped, we know that it is more likely to erupt."

At the briefing, Canfield was accompanied by Alphonse Sterling, an employee of the Naval Research Laboratory and a member of the Yohkoh science team, Sarah Gibson of the University of Cambridge in England, and David M. Rust of the Johns Hopkins University Applied Physics Laboratory in Laurel. Canfield is lead author of a paper to be published in the March 15 issue of Geophysical Research Letters.

Sterling and Hugh Hudson, working at the Institute of Space and Astronautical Science in Japan, in 1997 and 1998 were first to establish the significance of the sigmoid shape as a warning.

Now Canfield, Hudson and Montana State's David McKenzie have found a definite statistical correlation. They converted two years' worth of daily X-ray images from Yohkoh – 50 images per day – into movies they could analyze. Their study showed not only that "S marks the spot of a likely eruption," Sterling said, but also that the eruptions are tied to the large, dark features known as sun spots and other effects caused by forces welling up from deep inside the sun.

The findings require further work before they can be used effectively as a predictive tool, the researchers said. NASA's planned Solar Terrestrial Relations Observatory (STEREO) is designed to make three-dimensional images that should help with this process, and NOAA plans to launch a spacecraft similar to Yohkoh next year.

In 1995, a joint commerce, research and military task force sponsored by the National Science Foundation issued a National Space Weather Program Strategic Plan. Noting that the country's reliance on technological systems "is growing exponentially," the panel recommended the development of improved forecasting.

There already are signs that transformers are failing at an above-average rate in areas of the United States such as the Northeast that are particularly prone to geomagnetic disturbances, resulting in replacement costs that could total hundreds of millions of dollars, according to John G. Kappenman of Minnesota Power. But cause-and-effect evidence is unclear, in part because utilities have not done long-term monitoring of such problems.

NOAA's Heckman said increased warning time could greatly benefit space station astronauts planning spacewalks, who could face increased hazard during a major storm. And, by altering Earth's atmosphere, the events can cause military trackers of space debris to "misplace" orbiting hardware because of increased drag. "In the 1989 disturbance," he said, "over 5,000 significant objects were misplaced for two weeks."