These figures show a simulation of the magnetic field of the Earth, from deep within the Earth's core, reversing itself.
Gary A Glatzmaier (Los Alamos National Laboratory) and Paul H Roberts (University of California, Los Angeles). For more detail about the simulated geomagnetic reversal see Nature (1995) 377, 203-209.

# Magnetic Field Reversals

The magnetosphere can flip its orientation, so that the field lines which were pointed toward the north pole change and point toward the south pole. Then the south pole becomes the north pole, etc.

On Earth, the record of the reversal of the magnetic field is preserved in magnetic rocks which lie along the ocean floor. The magnetism preserved in these rocks points first in one direction, then in another direction, giving the ocean floor a stripped appearance (from a magnetic point of view). This means that many times in the past the north pole has become the south pole, and vice versa. Since no one knows how long this can take, no one can say whether it could happen over night or take thousands of years! This picture shows where the poles are currently found, and also shows that the poles drift over the surface of the Earth over time.

A planetary magnetic field is very complicated, generated in the core by a mixed up jumble of current, and is not as simple as a magnet.

The figure shows a magnetosphere configured with the (blue) field lines directed toward the north pole. Over a period of time, the magnetic field reverses itself such that the (blue) field lines are directed toward the south pole.

Mathematical theory suggests that the reversal of the field starts in the core of a planet when currents which generate the magnetic field cause the field to wrap around itself too many times.

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## The Magnetic Field

The force of magnetism causes material to point along the direction the magnetic force points. This property implies that the force of magnetism has a direction. As shown in the diagram to the left, the...more

## Planetary Magnets

The Earth is a good example of a planetary dipole, where the lines of force point in a direction out of the South (magnetic) Pole and into the North (magnetic) Pole. Planets can also show evidence of quadrupoles...more

## The Earth's Magnetosphere

The Earth has a magnetic field with north and south poles. The magnetic field of the Earth is enclosed in a region surrounding the Earth called the magnetosphere. As the Earth rotates, its hot core generates...more

## Earth's Magnetic Poles

Earth has a magnetic field. If you imagine a gigantic bar magnet inside of Earth, you'll have a pretty good idea what Earth's magnetic field is shaped like. Of course, Earth DOESN'T have a giant bar magnet...more

## Magnetosphere

A magnetosphere has many parts, such as the bow shock, magnetosheath, magnetotail, plasmasheet, lobes, plasmasphere, radiation belts and many electric currents. It is composed of charged particles and...more

## The Discovery of the Radiation Belts

The belts of trapped radiation above the Earth's atmosphere, but within the magnetosphere, were first detected by James Van Allen in 1958. Therefore these belts are also known as Van Allen Belts. When...more

## Earth's North Magnetic Pole

Earth has a global magnetic field that is approximately, though not exactly, a dipole field (like a bar magnet) with a north pole and a south pole. Earth's North Magnetic Pole (NMP) is not in the same...more

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