Cracks allow damage from solar storms

WASHINGTON — Earth's magnetic field can develop large cracks during solar storms, leaving parts of the atmosphere more susceptible to damage from solar wind, scientists reported Wednesday.

"We discovered that our magnetic field is drafty, like a house with a window stuck open during a storm," Harold Frey, an associate research physicist at the University of California-Berkeley and lead author of a study on the findings, said at a news conference at NASA headquarters.

"The house deflects most of the storm, but the couch is ruined. Similarly, our magnetic shield takes the brunt of space storms, but some energy continually slips though its cracks, sometimes enough to cause problems with satellites, radio communication and power systems."

The study was published Thursday in the journal Nature.

Scientists know that blasts of solar energy aimed toward Earth are more likely to be disruptive if the solar wind has a magnetic field that's oriented in the opposite direction to Earth's field. A process called "magnetic reconnection" causes part of Earth's magnetic shield to buckle and crack.

The magnetic field extends tens of thousands of miles, forming a protective barrier against the strongest radiation and magnetic effects of solar wind. But when the sun periodically spews out clouds of electrified gas at millions of miles an hour, Earth's magnetosphere becomes bent and buckled, and more energy can reach the upper atmosphere and the planet's surface.

Solar storms that reached Earth in October and November had some of the strongest energy levels on record. However, they were less damaging than feared because the wind's magnetic orientation was benign.

Predicted in theory more than 40 years ago, the cracks were confirmed in 1979 when a satellite briefly passed through one of the holes. But it was unclear whether the cracks were a fleeting phenomena or if they remained open for a sustained period of time.

Ultraviolet images captured by satellites during solar storms in 2000 and 2002 revealed large areas — one about the size of California — where solar wind was freely bombarding the lower atmosphere over the high Arctic region for as long as nine hours.

"The new knowledge that the cracks are open for long periods, instead of opening and closing sporadically, can be incorporated into our space-weather forecasting computer models to more accurately predict how our space weather is influenced by violent events on the sun," Tai Phan, another Berkeley research physicist who took part in the study, said at the news conference.

However, space-weather forecasters note that while Earth- and space-based instruments now can give days' notice that a solar storm is headed our way, there are no sensors yet in orbit that can alert scientists to a flare's magnetic alignment before it actually hits Earth's magnetosphere.

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On the Net: http:/www.nasa.gov; www.nature.com