Geomagnetism

Magnetic field overview

The geomagnetic field protects the Earth's atmosphere against charged particles from the solar wind. Rapid and long-term changes in the field are monitored by low-orbiting satellites and a global network of about 200 magnetic observatories. Field models, computed from these measurements, provide the direction and strength of the magnetic field at any desired location. Magnetometers (or a simple compass) can then be used to compute pointing directions, complementing the location information provided by the global positioning system (GPS).

The primary contributions to the geomagnetic field are

• The main field from the Earth's core
• Core flow inferred from the secular variation of the magnetic field
• The lithospheric field caused by magnetized crustal rocks
• Motional induction in the oceans
• Tsunami-generated magnetic fields
• Ionospheric fields
• Magnetospheric fields

For animations showing the change of the main magnetic field over the past centuries:

• Historical main field change and declination