Earth Takes a `One-Two Punch' From a Solar Magnetic Cloud

A vast magnetic cloud erupted from the sun and collided head-on with Earth at a million miles an hour earlier this month, delivering a "one-two punch" to Earth's magnetic field and, some scientists say, possibly causing the catastrophic failure of a $200 million AT&T communications satellite.

This powerful solar belch might have passed largely unnoticed but for a new international fleet of satellites now in position to study the "space weather" that flows regularly from the sun and sometimes disrupts communications systems, military radar and other electronic systems. The satellites saw it coming, making this the first such eruption to be recorded from beginning to end by scientific instruments.

First observed in the early 1970s, these eruptions, known as "coronal mass ejections," may occur as often as once a day when the sun is in its most active phase and pose no known immediate danger to human health. The latest drama began at 11 a.m. EST on Jan. 6, when the joint NASA-European Space Agency satellite SOHO first detected the eruption of magnetic particles -- essentially the sun's own substance -- blasting out of the sun's outer atmosphere, or corona, scientists said at a briefing yesterday.

As the big bubble raced toward Earth, it was so large that it took more than a day to pass any given point. SOHO and NASA's WIND, another satellite stationed between Earth and the sun, recorded the eruption in a series of time-lapse images, as well as measuring its velocity and other aspects. WIND data showed that the cloud was 30 million miles thick.

On Jan. 10, right on the schedule predicted by researchers, the big bubble hit Earth's magnetic field, mashed it briefly toward the planet's surface (and toward the orbital altitudes of some satellites) like a fist hitting a balloon, engulfed Earth and rolled on into interplanetary space.

It kicked up the energy intensity in Earth's natural radiation belts to more than 100 times normal, by one estimate, where it remained for several days.

At that point, said SOHO scientist Barbara Thompson, of the University of Minnesota, she got hundreds of e-mail messages and phone calls from scientists around the world, saying, "I think it's here."

A magnetic storm triggered by the event hit the south polar region early on the morning of Jan. 10, according to the British Antarctic Survey, disrupting communications and grounding aircraft for much of the day.

The cloud created "a one-two punch," said Robert Hoffman, lead scientist for the POLAR satellite (inside Earth's magnetosphere) at yesterday's briefing at NASA's Goddard Space Flight Center in Greenbelt. First the cloud of highly energetic electrons and protons poured energy into the magnetosphere, releasing energy explosively as magnetic sub-storms and pumping up the radiation belts. Then, early on Jan. 11, unexpectedly, a "huge pressure pulse" at the trailing edge of the bubble hit Earth, he said.

This pulse was actually an unusually dense region, where up to 200 times more highly energetic particles -- including "killer electrons" that can spawn even more destructive X-rays -- were packed into each square inch than in the rest of the cloud.

"It was essentially like it [Earth's magnetosphere] was hit with a hammer," Hoffman said, jacking the energy in the radiation belts up even further. "This rang the magnetosphere of Earth like a bell."

The amount of electrical current dumped into Earth's magnetic field by this event totaled a million amps. For those who have had to change the fuses in their basements, said Stephen P. Maran, an assistant director of space science at Goddard, "this would have blown 67,000 15-amp fuses."

The AT&T Telstar 401 satellite -- located in the affected area of the magnetic field -- suddenly fell silent on Jan. 11, cutting TV coverage to millions of U.S. viewers. Six days later, after unsuccessful attempts to reestablish contact, the company declared it permanently out of service.

Some 20 satellites stationed around Earth and out toward the sun, as well as 30 ground-based instruments around the globe, were used by scientists from a dozen countries to monitor the event for the International Solar Terrestrial Physics Program (ISTP). Coincidentally, on the day of the eruption, a number of participants in the project had gathered at Goddard to discuss ways of predicting space weather when scientists attending the meeting produced movies of the newborn mass coronal ejection. They then eagerly predicted the cloud's arrival time at Earth and other particulars.

Scientists at yesterday's briefing cautioned that they can make no official comment on the cause of the AT&T satellite failure because of legal and insurance issues involved. But some said privately that the intense radiation produced as the solar cloud hit Earth's radiation belts could have "fried" even radiation-hardened chips inside a satellite's system.

Space scientist Geoff Reeves, of the Los Alamos National Laboratory, reported that a similar meeting of Air Force, National Oceanic and Atmospheric Administration, the National Science Foundation and NASA scientists in Boulder, Colo., at the time of the eruption reached similar conclusions. "Although it is not known exactly what happened to the satellite," he said, the scientists developed a remarkably complete picture of what happened and "how that might have `killed' a $200 million satellite."

An AT&T spokesman said the three-year-old satellite -- whose anticipated life was 12 years -- was insured. Other sources told trade publications that the insured value was $134 million.

The Russian space station Mir and the space shuttle, as well as a number of satellites, orbit below the level where the effects from the radiation belts are dangerous, scientists said.

Solar experts believe the eruptions might be caused by sudden disruptions in the sun's own stable magnetic field, as field lines stretch and twist like titanic rubber bands and then snap. The sun is currently in a period of relatively low activity. Scientists said they can hardly wait for the buildup to "solar maximum" over the next three or four years.

The most disruptive recent solar weather event occurred during the last period of maximum solar activity, in March 1989, and knocked out power systems around Quebec. This month's event was smaller.

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