PSC.edu: Magnetic Flip-Flops

Magnetic Flip-Flops

Considering that ships, planes and Boy Scouts steer by it, Earth’s magnetic field is less reliable than you’d think. Rocks in an ancient lava flow in Oregon suggest that for a brief erratic span about 16 million years ago magnetic north shifted as much as 6 degrees per day. After little more than a week, a compass needle would have pointed toward Mexico City.

The lava catches Earth’s magnetic field in the act of reversing itself. Magnetic north heads south, and — over about 1,000 years — the field does a complete flip-flop. While the Oregon data is controversial, Earth scientists agree that the geological evidence as a whole — the “paleomagnetic” record — proves such reversals happened many times over the past billion years.

“Some reversals occurred within a few 10,000 years of each other,” says Los Alamos scientist Gary Glatzmaier, “and there are other periods where no reversals occurred for tens of millions of years.” How do these flip-flops happen, and why at such irregular intervals? The geological data, invaluable to show what happened, registers only a mute shrug when it comes to the deeper questions.

For that matter, why is it that instead of quietly fading away, as magnetic fields do when left to their own devices, Earth’s magnetic field is still going strong after billions of years? Einstein is said to have considered it one of the most important unsolved problems in physics. With a year of computing on Pittsburgh’s CRAY C90, 2,000 hours of processing, Glatzmaier and collaborator Paul Roberts of UCLA took a big step toward some answers. Their numerical model of the electromagnetic, fluid dynamical processes of Earth’s interior reproduced key features of the magnetic field over more than 40,000 years of simulated time. To top it off, the computer-generated field reversed itself…..Learn More

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Posted by Jose Reyes on Mar 10 2011. Filed under Post To Slider, Science News. You can follow any responses to this entry through the RSS 2.0. You can leave a response or trackback to this entry