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Earth's Magnetic Field

Providing geomagnetics reference information.

The Earth’s self-sustaining magnetic field is caused by motion of the liquid core of the Earth. This magnetic field extends several tens of thousands of kilometres into space, and protects us from the effects of solar wind.

Slow changes of the earth’s magnetic field are caused by changes in the core, which we cannot yet predict, so can only monitor. Over a long period, the average positions of the magnetic poles coincide with the geographic poles, but they wander significantly and the two magnetic poles are not at directly opposite positions on the globe. At intervals that are usually of hundreds of thousands to millions of years, the North and South magnetic poles interchange.

geomagnetics globe

Rapid fluctuations in the measured field are due to the particles and electromagnetic waves from the sun, and large solar disturbances can damage electronic and electrical systems, and are particularly dangerous to satellites and space travellers.

The description of the magnetic field requires measurements spread around the globe. Increasingly, long-term variations are studied by satellite observations, but fixed observatories are essential for studying rapid changes.

The GNS Science geomagnetics team measures and monitors the magnetic field primarily as a contribution to International Science, including “Space Weather” warnings of solar disturbances, but the observatory also provides reference information for various kinds of magnetic surveys.

The observatories in New Zealand and Samoa provide the only continuous data from about a 90° arc of the Southern Hemisphere, one eighth of the globe. Their continuing operation is essentially a contribution to the world scientific community.

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