Stormy weather in space

Sun sends immense magnetic cloud hurtling at Earth.

Scientists again warned that communications on Earth could be disrupted this week by another spectacular eruption on the surface of the sun and that it might even hamper firefighting efforts in California.

"It's headed straight for us like a freight train," said John Kohl, a solar astrophysicist at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass. "This is the real thing."

Predictions are it could strike Earth's magnetic field by midday today.

But the news isn't all bad: Strong geomagnetic storms can produce colorful auroras in the night sky visible as far south as Texas and Florida beginning late tonight.

The explosion of gas and charged particles into space from the corona, the outermost layer of the sun's atmosphere, isn't harmful to people. But it can knock out satellite communications, which some emergency crews are relying on in battling California's wildfires.

Similar solar events in recent years have disrupted television transmissions, GPS navigation, oil pipeline controls and even the flow of electricity along power lines.

Space weather forecasters warned of that possibility last week, when a previous solar flare erupted, and then they saw a new sunspot region developing in another part of the sun.

The cloud of charged particles from last week's eruption struck Earth "with only a glancing blow," Kohl said. It disrupted some airline communications.

But Kohl said scientists observed the biggest such explosion in 30 years shortly before 6 a.m. Tuesday. It produced a particle cloud 13 times larger than Earth and hurtled through the solar system at more than 1-million miles per hour.

The resulting geomagnetic storm could be ranked among the most powerful of its kind and last for 24 hours.

It is expected to disrupt the communications satellites and high frequency radios.

Federal researchers said they have turned off instruments and taken other precautions with science satellites.

Sunspots and solar storms tend to occur in 11-year cycles; the current cycle peaked in late 2000.

Scientists compared the latest flare to the "Bastille Day storm" that occurred in July 2000.

"The Bastille Day storm produced considerable disruption to both ground and space high-tech systems," said Bill Murtagh, a space weather forecaster for the National Oceanic and Atmospheric Administration.

Solar flares are intense, temporary releases of energy. They are seen at ground-based observatories as bright areas on the sun in optical wavelengths and as bursts of noise at radio wavelengths; they can last from minutes to hours. Flares are the solar system's largest explosive events and can be equivalent to about 40-billion Hiroshima-size atomic bombs.

- Source: National Oceanic and Atmospheric Administration's Space Environment Center.

© 2006 • All Rights Reserved • St. Petersburg Times 490 First Avenue South • St. Petersburg, FL 33701 • 727-893-8111 Contact the Times | Privacy Policy Standard of Accuracy | Terms, Conditions & Copyright