What is the use of the earth's magnetic field

The Earth's magnetic field, in simple terms, is analogous to placing a magnet rod at the center of the Earth, with the N pole roughly facing the geographic South Pole and the S pole roughly facing the geographic North Pole. The magnetic poles don't exactly coincide with geography. There is a magnetic declination Angle of 11.5 degrees. Of course, the center of the earth is hot and there is no magnet rod, but the magnetic field is generated by the electric effect of electrons in the outer core as the earth rotates (similar to electromagnetism).
The magnetism of the earth is one of the physical properties of the earth's interior. The earth is a large magnet, forming a magnetic field around it, that is, the space showing the effect of magnetic force, called the geomagnetic field. It is similar to the magnetic field of a magnetic dipole located at the center of the earth, which is the most basic property of the geomagnetic field.

The Earth magnetic field is not isolated, it is affected by external disturbances. The solar wind is a stream of high-temperature, high-speed and low-density particles ejected from the sun's corona into interplanetary space, mainly composed of ionized hydrogen and ionized helium. The earth's magnetosphere is located at a height of 600 ~ 1000 kilometers from the top of the atmosphere. The outer boundary of the magnetosphere is called the magnetopause, which is 50 ~ 70 thousand kilometers from the ground. Under the compression of the solar wind, the earth's magnetic field lines extend far out into space on the side opposite the sun, forming a long tail called the magnetail. It was discovered in 1967 that a region of about 10 Earth-radius on either side of the neutral sheet is filled with dense plasma, known as the plasma sheet.

Usually matter with the number of positive and negative charges are equal, but due to the earth's core material by pressure, the temperature is higher also, inside there is a lot of ferromagnetic elements, material into power of plasma, which overcome the nucleus of the atom of gravity, become free electrons, and because of the core of the material by the huge pressure, free electrons tend toward the pressure lower mantle, making the core in the positively charged state, near the earth's mantle in a negatively charged state, is like a huge "atomic". Because of the huge size of the Earth's core and the relatively high temperature and pressure, the layer has a very high conductivity, which makes the current flow in it forever as if it existed in a coil with no resistance. This makes the Earth form a stable north and south magnetic pole of magnetic field strength.
As for the formation of the earth's magnetic field, one hypothesis about the formation of the earth's magnetic field holds that the formation of the earth's magnetic field is similar to the formation of the magnetic field of other planets. The earth or other planets are charged for some reason or lead to the uneven distribution of the charge between the layers. Since these charges move in a circle with the rotation of the planet, and since the moving charges are current, the current must produce a magnetic field.