Magnetic fields are created by moving particles.
The magnetic field is created by moving, therefore the concept itself arose in electrodynamics simultaneously with the concept of "electric field". It was introduced first by M. Faraday, and a little later by J. Maxwell, in order to explain why electric charges have such a relatively short range of interaction.
The fathers of electrodynamics believed that the field was created by the deformation of the ether - an invisible speculative environment that fills all things (Einstein, while working on the theory of relativity, abolished the concept of ether). Although it may seem strange to modern people, until the 20th century, physicists really did not doubt a certain substance that penetrates everything. The way the magnetic fields are created and what their nature is, physicists could not explain.
When the special theory of relativity (SRT) entered into use, and the ether was "officially removed", the space became "empty", but the fields even in a vacuum continued to interact,But this is impossible between intangible objects (at least according to the STR), so physicists have found it necessary to assign certain attributes to electric and magnetic fields. Such concepts as mass, momentum and energy of fields are created.
Magnetic field properties
Its first property explains the nature of its origin: a magnetic field can arise only under the influence of moving charges (electrons) of an electric current. The power characteristic of a magnetic field is called magnetic induction, it is present at any point of the field.
The impact of the field applies only to moving charges, magnets and conductors. It can be of two types: variable and constant. The magnetic field can be measured only with the help of special devices, it is not fixed by human senses (although biologists believe that some animals may perceive changes in it). The essence of another property of the magnetic field is that it has an electrodynamic nature, not only because it can only affect moving charges, but also because it is generated by the movement of charges.
How to see
Although human senses cannot detect the presence of a magnetic field, its direction can be determined with a magnetized arrow. However, you can “see” the magnetic field with a sheet of paper and simple iron filings. It is necessary to put a sheet of paper on a permanent magnet and sprinkle sawdust on top, after which iron shavings will line up along closed and continuous lines of force.
The directionality of the lines of force is determined using the right-hand rule, which is also called the “gimlet rule”. If you take the conductor in your hand in such a way that the thumb is in the direction of the current (the current moves from minus to positive), then the other fingers will indicate the direction of the power lines.
Magnetic fields are created by moving charges, but then what is the nature of geomagnetism? Our planet has a magnetic field that protects it from harmful solar radiation, and the diameter of the field is several times larger than the diameter of the Earth. In shape, it is not uniform, on the “sunny side” it shrinks under the influence of the solar wind, and from the night side it stretches in the form of a long wide tail.
It is believed that on our planet magnetic fields are created by the movement of currents in the core, which consists of a liquid metal. This is called the “hydromagnetic dynamo”. When a substance reaches a temperature of several thousand degrees Kelvin, its conductivity becomes high enough so that movements, even in an environment with weak magnetization, begin to create electric currents, which, in turn, create magnetic fields.
In local areas, magnetic fields are created by magnetized rocks from the upper layers of the planet that form the crust.
Since 1885, the registration of the movement of the magnetic poles began. Over the last century, the south pole (the pole in the southern hemisphere) has moved 900 kilometers, and the north (arctic) magnetic pole has moved 120 kilometers in 11 years, and in the next ten years, another 150 kilometers. Arctic pole increased from 10 kilometers per year to 60.
Although scientists know how the magnetic field of the Earth is created, they cannot influence the movement of the poles and assume that another inversion will happen pretty soon. This is a natural process, this is not the first time on the planet; however, it is not known how this process will turn out for people.