h's natural magnetic field has confirmed that the magnetosphere develops cracks that may last for hours. This breach allows charged electrons and ions from the sun, a force called the solar wind, to stream into the Earth's upper atmosphere and dump massive loads of magnetic energy.

Scientists have long known that the Earth's magnetosphere - the area of space just above Earth's ionosphere and controlled by Earth's magnetic field - occasionally develops cracks. The new satellite studies confirm for the first time that these cracks can last for hours, allowing a steady flow of solar wind into the upper reaches of the atmosphere.

"Our magnetic shield takes the brunt of space storms from the sun, but some energy continually slips through its cracks, sometimes enough to cause problems with satellites, radio communications and power systems," said Harald Frey of the University of California, Berkeley. He said the cracks means that the magnet shield is "like a drafty old house with a window open in a storm" that allows solar energy to penetrate to the Earth's upper atmosphere.

Frey and other researchers presented results of their study on Wednesday at a news conference at the headquarters of the National Aeronautics and Space Administration.

Nasas operates one of the satellites used in the research and is a partner with the European Space Agency on another satellite system that confirmed the findings. The study appears this week in the journal Nature.

Tai Phan, another University of California, Berkeley researcher and a co-author of the paper, said that this new understanding about how cracks develop in the Earth's magnetosphere will help scientists predict how eruptions on the sun will affect the planet.

A stream of electrically charged particles flows constantly from the sun, forming a force called the solar wind. A particularly violent solar event, called a coronal mass ejection, can send billions of tons of electrified gas toward the Earth at millions of kilometres an hour.

A magnetic field that surrounds the Earth and extends tens of thousands of kilometres into space protects the planet from most of the violence of the solar blasts. But a small percentage of the energy can penetrate the shield, causing auroras. More powerful blasts, teamed with the magnetosphere cracks, can allow bursts of magnetic energy to reach the Earth.

If these solar storms are powerful enough, they can disrupt some radio communications, damage satellites and even cause power grids to short out. The solar energy bursts can also threaten orbiting astronauts.

Researchers hope to refine techniques to predict solar storms and their effect on Earth in order to warn satellite and power grid operators and allow astronauts in space to seek protection in sheltered modules.

- Sapa-AP

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