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.

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

Flip-Flop

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.

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.