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Earth’s magnetic field

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Earth’s magnetic field is the magnetic field that surrounds Earth. It arises from the interaction between moving charges in Earth’s core and the surrounding environment.

It creates the magnetosphere, which is the region around Earth where the magnetic field is present. The magnetosphere shields Earth from cosmic radiation.

Some animals, such as birds and fish, use Earth’s magnetic field for spatial orientation.

Earth’s magnetic field has the form of a dipole, meaning it has two poles:

  • North: The north pole is located in Canada.
  • South: The south pole is in Antarctica.

Earth’s magnetic poles are not fixed. They constantly move, and their locations can change by several kilometers per year. Additionally, Earth’s magnetic field is not a perfect dipole. It has a number of complex non-uniformities that can affect its strength and direction.

Earth's magnetic field

Simplified, Earth’s magnetic field can be envisioned as the field of a magnetic dipole tilted at an angle of approximately 11.5° relative to Earth’s rotation axis and displaced about 300 km from Earth’s geomagnetic center.


Several types of Earth’s magnetic field are distinguished:

  • Main: Caused by mechanical-electromagnetic processes in Earth’s outer core.
  • Anomalous: Primarily related to the magnetization of rocks in the Earth’s crust.
  • External: Resulting from electric currents in the near-Earth space and induced in Earth’s mantle; it has a pronounced latitudinal distribution (more intense in polar regions and decreasing towards the equator).

Factors influencing Earth’s magnetic field include:

  • Solar activity: Solar flares and solar wind can induce changes in Earth’s magnetic field.
  • Ozone layer depletion: Depletion of the ozone layer can lead to increased cosmic radiation reaching Earth, which in turn can cause changes in Earth’s magnetic field.
  • Geological processes: Geological processes in the core can also affect the magnetic field.

History of Research

Chinese and Mongols recognized the north direction of magnetized objects over a thousand years ago. The first qualitative measurements of Earth’s magnetic field components, such as declination and inclination, became possible and known after the invention of the dry compass in the 12th century.

In 1600, English physician and natural philosopher William Gilbert published his work “De Magnete”, where he first recognized that Earth is the cause of compass needle alignment. Measurements by Henry Gellibrand in London also showed that the magnetic field is not static but changes slowly.

Alexander von Humboldt conducted systematic measurements in Prussian mining industry and during his exploratory travels. Carl Friedrich Gauss built the first geophysical observatory in Göttingen and constructed a sensitive magnetometer for it in 1832. He understood that globally distributed measurements should be conducted simultaneously to localize the causes of fluctuations and measure the static field more accurately. From 1836, the Magnetic Association, founded for this purpose, and the Royal Society provided data he and Wilhelm Weber evaluated. By 1839, he was able to show that most of Earth’s static magnetic field originates from inside Earth, while smaller, short-term fluctuations in Earth’s magnetic field originate from outside.

Further international measurement campaigns took place during the polar years of 1882, 1932, and the International Geophysical Year 1957–1958. Previous mechanical magnetometers (magnetic field balances, torsion magnetometers) were increasingly replaced by inductive or atomic magnetometers (saturation core, ferrozond (Forster probe); proton and cesium).

From an industrial history perspective, the development of appropriate precise measuring devices in Germany in cooperation with scientific research was closely related to Askania’s work in Potsdam, such as Schmidt’s field scale, which is used worldwide and which, in addition to measuring regional data on the magnetic field, also allowed the estimation of magnetization of rock samples.

Earth’s magnetic field plays an important role in ensuring the stability and protection of the planet. It affects compasses and navigation systems and also provides protection for the atmosphere from the harmful effects of solar wind, assists in scientific research of natural processes, and in the study of geology.