The Earth

Magnetic Field of the Earth, Origin and Characteristics

Magnetic field of the Earth, origin and characteristics

The Earth's magnetic field is the magnetic field generated by the internal activity of the Earth. It is also known as the Earth's geomagnetic field.

The magnetic field protects the planet from ionizing radiation from the solar wind. The zone of influence of the Earth's magnetic field in space, which extends many thousands of kilometers into space, is called the magnetosphere.

The Earth's magnetic field acts as a protective shield for the planet. The magnetic field protects us from energy-charged particles from the Sun (photons) and from cosmic radiation. 

Recently a weakening of the Earth's magnetic field has been observed. Some research estimates that the Earth's magnetic field has lost about 9% of its strength in the last 200 years.

What Is the Origin of the Earth's Magnetic Field?

There are different theories about the origin of the Earth's magnetic field but none of them is definitive. However, the theory that is best accepted is that of the generation of the magnetic field by the dynamo effect.

This dynamo theory is based on the fact that a conductive material in a liquid state, when in motion, can generate a magnetic field like that of planet Earth.

The core of the Earth is made up of metallic materials in a liquid state (in particular, liquid iron and nickel) that undergo convective movements.

The early earth's magnetic field would originate from the sea of ​​magma that is believed to have enveloped the planet. Because this magma would be subjected to very high temperature and pressure, it could generate enough electrical conductivity to generate the dynamo effect as a result of the movement of electrically charged particles.

What Are the Three Parts of the Earth's Magnetic Field?

The geomagnetic field is made up of three parts, the first two belong to the internal field and the third to the external one:

  • The nuclear field is the one that is produced inside the Earth. This field changes relatively slowly and originates in the outer core by systems of electrical currents. Their contribution to the total field is greater than 94%.
  • The field of the crust, generated by rocks magnetized by the nuclear field.
  • The external or atmospheric field and the internal induced field. The first is generated by electric currents produced in the Earth's atmosphere by interaction of the magnetic field with the solar wind and the second by a field induced in the crust and mantle by the same currents.

What Is the Earth's Magnetic Field Like?

The Earth behaves like a giant magnet and has magnetic poles, which do not coincide with the geographic poles.

By definition, a magnetic pole is a point where the geomagnetic field generated by a magnetic dipole placed in the outer core of the earth has a direction that coincides with the axis of the dipole, that is, vertical.

However, the nomenclature that defines the north and south magnetic poles is just a convention. The Earth's magnetic north and south poles have been named in association with the geographic one. However, the geographic axis and the magnetic axis do not coincide.

While the geographic poles are fixed, the magnetic ones are subject to a continuous, slow, non-constant and different displacement for each one of them.

The geographic north and south poles differ from the respective magnetic poles by almost 3000 km. The south magnetic pole is farthest from the magnetic north pole.


Published: October 7, 2021
Last review: October 7, 2021