Thursday, July 10, 2008

Earth's Core, Magnetic Field Changing Fast, Study Says

Kimberly Johnson
for National Geographic News
June 30, 2008

Rapid changes in the churning movement of Earth's liquid outer core are weakening the magnetic field in some regions of the planet's surface, a new study says.

"What is so surprising is that rapid, almost sudden, changes take place in the Earth's magnetic field," said study co-author Nils Olsen, a geophysicist at the Danish National Space Center in Copenhagen.

The findings suggest similarly quick changes are simultaneously occurring in the liquid metal, 1,900 miles (3,000 kilometers) below the surface, he said.

The swirling flow of molten iron and nickel around Earth's solid center triggers an electrical current, which generates the planet's magnetic field.

(Learn more about Earth's interior.)

The study, published recently in Nature Geoscience, modeled Earth's magnetic field using nine years of highly accurate satellite data.


Fluctuations in the magnetic field have occurred in several far-flung regions of Earth, the researchers found.

In 2003 scientists found pronounced changes in the magnetic field in the Australasian region. In 2004, however, the changes were focused on Southern Africa.

The changes "may suggest the possibility of an upcoming reversal of the geomagnetic field," said study co-author Mioara Mandea, a scientist at the German Research Centre for Geosciences in Potsdam.

Earth's magnetic field has reversed hundreds of times over the past billion years, and the process could take thousands of years to complete.

(Related story: "Magnetic Field Weakening in Stages, Old Ships' Logs Suggest" [May 11, 2006])

Upper Atmosphere Radiation

The decline in the magnetic field also is opening Earth's upper atmosphere to intense charged particle radiation, scientists say.

Satellite data show the geomagnetic field decreasing in the South Atlantic region, Mandea said, adding that an oval-shaped area east of Brazil is significantly weaker than similar latitudes in other parts of the world.

"It is in this region that the shielding effect of the magnetic field is severely reduced, thus allowing high energy particles of the hard radiation belt to penetrate deep into the upper atmosphere to altitudes below a hundred kilometers (62 miles)," Mandea said.

This radiation does not influence temperatures on Earth. The particles, however, do affect technical and radio equipment and can damage electronic equipment on satellites and airplanes, Olsen of the Danish space center said.

Keep Watching

The study documents just how rapidly the flow in Earth's core is changing, said Peter Olson, a geophysics professor at Johns Hopkins University in Baltimore, Maryland, who was not involved with the research.

By using satellite imagery, researchers have a nearly continuous measurement of changes, he said.

"They provide a good rationale to continue this monitoring longer," Olson said.

Earth's core fluid affects magnetic field
United Press International - Jul 9, 2008
Olsen and Mandea say their model for the flow at the top of the Earth's core fits with recent rapid changes in the planet's magnetic field, and is also in ...

Wayne Hale's NASA Blog: Serendipity - Part 3
Space Ref (press release) - 14 minutes ago
The Earth's large core and mantle generate the magnetic field. Venus, although almost the twin of Earth in total size and mass, does not have nearly as ...

Rapid changes in Earth's core affecting the planet's magnetic field
Smash Hits, India - Jul 8, 2008
The very precise measurements of the Earth's magnetic field delivered by the geosatellite CHAMP, combined with Orsted satellite data and ground observations ...


ABC News
New Mercury Images Show Volcanoes, Magnetic Field, More
National Geographic, DC - Jul 3, 2008
They also shed more light on Mercury's magnetic field, which mirrors Earth's on a tiny scale. And they reveal widespread slip faults, relics of a time when ...
Flyby of Mercury Answers Some Old Questions New York Times
Mercury Flyby Reveals Active (but Shrinking) Core Scientific American
Mercury's core still active, scientists say
eFluxMedia - Rocky Mountain News
all 194 news articles »

No comments: