Earth's magnetic field

characteristics
- Has a predominantly dipole nature;

- shows temporal variability;

- now the axis is offset from earth's rotational axis but over time the magnetic axis is parallel to the rotational axis;

- reverses on time scale 10,000 to 100,000 years.

In last 40 years have arrived at a plausible generating mechanism - the geodynamo. The electrically conductive outer core acts like a dynamo or generator. As the outer core fluid rotates relative to rotating Earth as a whole, and also convects, electrical currents cut across existing magnetic lines of force. This regenerates the geomagnetic field at the expense of the fluid core's kinetic energy.

How do the magnetic field flip-flops happen? 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.

Studies of the record of Earth's magnetic field preserved in rocks provided key information leading to the Plate Tectonic Model.

Click here to access a site to help with understanding the role of paleomagnetic studies in plate tectonic studies.

More detailed information on Earth's magnetic field

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