Sun hurls magnetic storm at Earth Energy can disrupt communications, electrical systems

April 10, 1997|By Frank D. Roylance | Frank D. Roylance,SUN STAFF

A storm of magnetic energy -- the second since January -- began sweeping past Earth late yesterday, threatening to disrupt vulnerable radio communications and electric power systems today or tomorrow.

Alerted by a fleet of solar observatories, federal officials were advising vulnerable industries, such as power companies and communications satellite operators, to take whatever precautions they could.

A similar, smaller solar magnetic storm in January is thought to have silenced a $200 million Telstar communications satellite, interrupted radio communications at an Antarctic base and triggered auroral displays.

People, even the astronauts inside the Mir space station, were not in any physical danger, thanks to the shelter provided by Earth's magnetic field, scientists said.

But such storms can alter that magnetic field, and some life forms sensitive to these changes might be affected.

"We get calls from pigeon racers. When there are variations in the [Earth's] magnetic field, pigeons get lost," said Mike Schmeiser, duty forecaster at the federal Space Environment Center in Boulder, Colo., which issued the advisories.

Increased auroral displays were likely, perhaps as far south as the northern tier of the United States, scientists said.

The colorful, shimmering auroras occur when atomic particles racing from the sun are drawn to the poles by Earth's magnetic field. There they encounter the upper reaches of the atmosphere and cause gas molecules to glow.

The latest solar storm began at 10 a.m. Monday, when billions of tons of gas and atomic particles suddenly erupted from the surface of the sun. They raced off into space in a vast bubble expanding at more than 2.2 million mph.

Coronal mass ejections are not uncommon. Since it was launched in December 1995, NASA's sun-orbiting Solar and Heliospheric Observatory (SOHO) has reported one every four or five days on average, said Dr. Mauricio Peredo, head of science planning at the Goddard Space Flight Center for the International Solar Terrestrial Physics program.

Of these, only six or seven have erupted from a portion of the sun's surface facing the Earth. But there will be more in the next few years, Peredo said.

"We are now close to the solar minimum," he said, referring to a quiet period in the sun's 11-year cycle of activity. "As we approach solar maximum, near the year 2000, we will see something like one or two [coronal mass ejections] per day. There will definitely be more of these events, and also larger in nature."

A big one in 1989 triggered widespread power outages in Canada's Quebec province.

Monday's event began with what Schmeiser called a "mundane kind of middle-of-the-road [solar] flare." Solar flares are short, high-temperature outbursts on the sun associated with sunspots.

Monday's flare was rated as a C6 on a scale that measures X-ray emissions, Schmeiser said. A events are the smallest, B events are 10 times bigger, and C eruptions are 100 times larger than A's.

Solar scientists elsewhere were more enthusiastic.

Dr. Guenter Brueckner, of the Naval Research Laboratory in Washington, principal investigator for one of SOHO's key instruments, said solar flares are not always indicative of the size of any accompanying coronal mass ejections.

"The January event didn't have a flare at all," he said.

Dr. Donald J. Michels, head of the coronal physics section at the Naval Research Lab, referring to Monday's event, said, "We've never seen a coronal mass ejection so big, bright and full of complex details" since SOHO was launched.

Dr. Barbara Thompson, a research scientist on the SOHO team at Goddard, said the pictures drew a reaction of "Holy cow! It's beautiful," from some of the 150 solar scientists gathered from around the world this week for a conference at Goddard on the January solar storm.

"It was their first time to see something as stark and dramatic as this event," she said.

Although solar scientists have been observing the sun for decades, they have never had so many highly sensitive instruments to work with. There are at least 14 satellites contributing to the International Solar Terrestrial Physics Program and perhaps 40 ground observatories.

"All our sensors are up there and working, and for the most part working beautifully," he said.

But the experts are still gathering the experience they need to interpret what they see and to predict the effects on Earth.

Scientists now know how the January event affected Earth's magnetic field and communications, Michels said. But "the event we saw in January was significantly different from the event we saw Monday. Everybody is all up on ready-alert, waiting to see what happens."

The storm front that headed for Earth this week was traveling at 2 million mph, Thompson said. January's moved at a relatively sedate 1 million mph. "This event also appears to be more massive," he said.

Because telemetry from the satellite outposts was not due for transmission to Earth until 3 a.m. today, it was not immediately clear whether the magnetic storm would strike Earth head-on or pass with just a glancing blow.

Schmeiser, at the Space Environment Center, said the eruption left the sun from a region 29 degrees below the sun's equator, so much of its energy may pass well south of Earth.

Pub Date: 4/10/97

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