Magnetism is a phenomenon where magnets attract or repel magnets in their magnetic field. The magnetic field is the region around a magnet where it exerts its magnetic effect of either attracting or repelling a magnet. Our planet earth is also known to exert the phenomenon of magnetism. 

The magnetic field of the earth is also known as the geomagnetic field and is similar to that of a bar magnet. The magnetic field of the earth is known to develop from the core of the earth, which contains iron in it. There is a famous theory of earth’s magnetism known as the dynamo theory. 

Introduction to the magnetism of the earth

Earth is a planet that is known to have its magnetism and a magnetic field. The magnetic field of the earth, also known as the geomagnetic field, is dipolar and extends millions of kilometres into outer space. The earth’s north magnetic pole is near the south pole, and the south magnetic pole of the earth is near the north pole. This is the main reason behind the fact that in a compass, the north pole is directed towards the north pole. 

The region of the earth’s magnetic field is known as the magnetosphere that is present above the ionosphere of the atmosphere. It can be represented in a 3D vector. It was Carl Friedrich Gauss who measured the strength of the earth’s magnetic field in 1832. 

Theory of Earth’s Magnetism

The dynamo theory is a well-accepted theory for earth’s magnetism and was proposed by Walter M. Elsasser and Edward Bullard in the mid-1900s. According to this theory, the outer core of the earth consists of iron in a molten state and many heavy metals in a liquid or aqueous state. 

The inner core of the earth, due to the effect of gravity, is considered to be solidified. Due to this, the metallic fluids present in the outer core are in a constant state of motion, which helps the earth to generate its magnetism.

Earth and Magnetism

There are various reasons behind earth’s magnetism, but the well-accepted explanation is the dynamo theory. Some of the other theories associated with earth’s magnetism are:

• Core surface flow– It is believed that 90% of the earth’s core is composed of iron which is a good conductor of electricity. The core is divided into two regions: the inner core and the outer core. According to this model, it is observed that liquid iron in the outer core flows, which can be predicted from the main field at the earth’s surface.
• Lithosphere Magnetisation– It is also believed that magnetisation of the lithosphere is also a reason behind the magnetic field of the earth. The reason behind the magnetisation of the lithosphere is thought to be the presence of magnetic minerals like magnetite and titanium. 
• Ocean tidal dynamo– It is known that ocean water is rich in ions and salts and is highly conductive. According to this theory, the movement of this ocean water due to the existing magnetic field of earth induces an electric field, and this electric field, in turn, generates a secondary magnetic field.
• Magnetosphere– It is a large cavity formed due to the earth’s magnetic field (a region where the earth’s magnetic field lines exist). The charged particles in the solar system cannot cross the magnetic field lines of the earth and are deflected. The interaction between the earth’s magnetic field and the solar winds leads to the formation of a multitude of electric currents. This is regarded as the magnetospheric current.

Significance of Earth’s magnetism

It is the earth’s magnetism that protects the atmosphere from solar winds.

The earth’s magnetism is used for designing satellites, which are used for various purposes. It can also be used to conduct research and study the tectonic plates, boundaries, and many other factors.

Conclusion

The magnetic field is the region around a magnet where it exerts its magnetic effect of either attracting or repelling a magnet. The magnetic field of the earth is also known as the geomagnetic field and is known to develop from the outer core of the earth, which contains molten iron in it. There is a most famous theory of earth’s magnetism, known as the dynamo theory, which explains the reason behind the magnetic field of the earth. Apart from this, a few more theories are present to explain the magnetism of the earth.