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Solar Storms Make the Sun a Real Star

Each eruption can disrupt electric utilities, communications and airplane travel.

November 16, 2003|Joseph B. Verrengia | Associated Press Writer

DENVER — Even astronomers can take the sun -- glowing steadily for more than 4 billion years and rising unfailingly every morning -- for granted. Among the 100 billion stars in the Milky Way, ours is rather lackluster.

But the sun certainly is demanding everyone's attention now, three weeks into perhaps the most dramatic and unexpected chain of eruptions ever observed venting from its seething, bubbling surface.

There have been as many as 11 salvos since Oct. 19. And the fireworks could reach a new crescendo by Thanksgiving, the nation's busiest holiday for air travel, just one of the things that may be disrupted.

"There's been nothing quite like this," said Bill Murtagh, a space weather forecaster for the National Oceanic and Space Administration in Boulder, Colo. "Another big blow is not what anyone needs."

NASA scientists compare it to a blizzard in July -- in California.

It sounds incredible, but "something like that just happened on the sun," said David Hathaway, a solar physicist at NASA's Marshall Space Flight Center in Alabama.

The biggest solar storm to affect Earth in the recent cycle was Oct. 28. It caused little damage, largely because it was forecast, and electric utilities and satellite companies took precautions.

Even so, it caused a blackout in Sweden, damaged two Japanese satellites, and upset radio communications and navigation systems for jets and ships. Airlines in the northern latitudes flew lower to protect passengers from extra doses of radiation.

It is a startling reminder of who's really in charge of the solar system. Scientists worry that a new round of eruptions could do more of the same or worse.

Each solar burst hurls into space huge clouds of superheated, charged particle clouds that are 13 times the size of Earth. A Nov. 4 explosion ranks as the most powerful solar flare to be recorded by orbiting instruments -- although it was pointed away from Earth.

"This period will go into the history books as one of the most dramatic," said Paal Brekke, deputy project scientist for the Solar & Heliospheric Observatory, a joint U.S.-European observatory between Earth and the sun.

What will the sun do next? Astronomers can only watch and wait.

Early civilizations from the Sumerians to the Aztecs worshipped the sun for its life-nourishing properties. Its furious dynamics weren't discovered until Galileo and others in the 17th century began to directly observe the sun through the first telescopes, sacrificing their eyesight for their discoveries.

In 1613, Galileo published three letters on sunspots, the cooler, dark, irregular spots that resemble cancerous moles on the sun's fiery face. By recording the sunspots' disappearance around the far side, Galileo was the first to demonstrate that the sun rotates.

But how do sunspots form and how do they trigger solar explosions? How do they affect Earth? Researchers still aren't sure.

The sun is not solid, but a dense and torrid ball of gas. It rotates in sections at different latitudes as if the layers of a cake were turning at different speeds, with the equator's layer moving faster than the poles.

This phenomenon tangles and twists the sun's magnetic field. The migration of hot plasma from the sun's interior dynamo up to the surface is somehow inhibited in these distortions, producing sunspots.

Sunspots erupt and fade in 11-year cycles. But that's just an average; some cycles last 15 years.

New studies suggest that sunspots also work in longer patterns of 100 and 1,000 years. The sun's luminosity can change slightly during those cycles, possibly affecting Earth's climate and, some argue, contributing to global warming. If true, those details will take years to work out.

The current 11-year solar cycle, No. 23, peaked quietly in 2000. By late 2003, it was supposed to be on its downside. Researchers were labeling it a dud.

Until now.

Sunspots' magnetic distortions intensify until something explodes. Some sunspots reload and fire again. And again. That is what's happening now with the current sunspot clusters, 484 and 486.

From 93 million miles away, they look like tiny smudges on the sun's chin. Yet each rival Jupiter in size.

Forecasters in Boulder are analyzing past cycles to determine whether powerful sunspots similarly have appeared late.

"In 1984, we had a bout of activity four years after the solar max in that cycle," Murtagh said. "What's different with Cycle 23 is today's events are more intense than what occurred at the cycle's maximum."

Sunspots are best known for spawning solar flares, which are akin to space tornadoes. They last for hours, extend for tens of thousands of miles and reach millions of degrees.

In recent years, astronomers have identified a second and even more powerful tempest -- the coronal mass ejection. Like a cosmic Molotov cocktail, that is the phenomenon that has been bombarding Earth lately.

A CME bursts from the sun's corona, the wispy, outermost and hottest layer. Often, CMEs trigger solar flares below too.

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