The Earth's magnetosphere it is the magnetic envelope of the planet against the current of charged particles that the Sun emits continuously. It is caused by the interaction between its own magnetic field and the solar wind.
It is not a unique property of the Earth, since there are many other planets in the solar system that have their own magnetic field such as: Jupiter, Mercury, Neptune, Saturn or Uranus..
This stream of matter that flows from the outer layers of our star, does so in the form of rarefied matter, called plasma. This is considered the fourth state of matter, similar to the gaseous state, but in which high temperatures have provided an electric charge to the particles. It consists mainly of protons and free electrons.
The solar corona emits these particles with so much energy that they can escape gravity, in a continuous flow. Is the call solar wind, which has its own magnetic field. Its influence extends throughout the Solar System.
Thanks to the interaction between the solar wind and the geomagnetic field, a transition zone is formed that encloses the Earth's magnetosphere.
The solar wind, which has a high electrical conductivity, is responsible for distorting the Earth's magnetic field, and compresses it on the side facing the Sun. This side is called day side. On the opposite side, or night side, the field moves away from the Sun and its lines stretch out forming a kind of tail.
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The solar wind modifies the Earth's magnetic field lines. If not for him, the lines would be expanded to infinity, as if it were a bar magnet. The interaction between the solar wind and the Earth's magnetic field gives rise to three regions:
1) Interplanetary zone, where the influence of the Earth's magnetic field is not perceptible.
2) Magnet-sheath or magneto-envelope, being the area where the interaction between the terrestrial field and the solar wind occurs.
3) Magnetosphere, is the region of space that contains the Earth's magnetic field.
The casing is limited by two very important surfaces: the magnetopause and the shock front.
The magnetopause is the boundary surface of the magnetosphere, approximately 10 Earth radii on the day side, but it can be further compressed, especially when large amounts of mass are shed from the solar corona..
For its part, the shock front or shock arc is the surface that separates the magneto sheath from the interplanetary zone. It is at this edge where the magnetic pressure begins to slow down the solar wind particles..
In the diagram of figure 2, in the magnetosphere or cavity that contains the earth's magnetic field, well-differentiated areas are distinguished:
- Plasma sphere
- Plasma sheet
- Magneto glue or magnetic glue
- Neutral point
The plasma sphere It is an area formed by a plasma of particles from the ionosphere. Particles coming directly from the solar corona that have managed to sneak in will also stop there..
All of them form a plasma that is not as energetic as that of the solar wind..
This region begins 60 km above the earth's surface and extends up to 3 or 4 times the earth's radius, including the ionosphere. The plasmasphere rotates alongside the Earth and partially overlaps with the famous Van Allen radiation belts..
The change in the direction of the earth's field due to the solar wind, originates the magnetotail, and also a confined zone between magnetic field lines with opposite directions: the plasma sheet, also known as current blade, several earth rays thick.
Finally the neutral point it is a place where the intensity of the magnetic force is completely canceled. One of them is shown in figure 2, but there are more.
Between the day and night part of the magnetopause there is a discontinuity, called cusp, where the lines of magnetic force converge towards the poles.
It is the cause of the northern lights, since the particles of the solar wind rotate in a spiral following the magnetic lines. Thus they manage to reach the upper atmosphere of the poles, ionizing the air and forming plasmas that emit brightly colored light and X-rays..
The magnetosphere contains appreciable amounts of plasma: a low-density ionized gas made up of positive ions and negative electrons, in proportions such that the whole is almost neutral..
The density of plasma is highly variable and ranges from 1 to 4000 particles per cubic centimeter, depending on the area..
The gases that originate the plasma of the magnetosphere come from two sources: the solar wind and the terrestrial ionosphere. These gases form a plasma in the magnetosphere made up of:
- Electrons
- Protons and 4% of [SEEMS INCOMPLETE]
- Alpha particles (helium ions)
Complex electric currents are created inside these gases. The current intensity of the plasma in the magnetosphere is approximately 2 x 1026 ions per second.
In the same way, it is a highly dynamic structure. For example, within the plasmasphere, the half-life of plasma is several days and its motion is primarily rotational..
On the other hand, in more external regions of the plasma sheet, the half-life is hours and its movement is dependent on the solar wind..
The solar wind comes from the solar corona, the outer layer of our star, which is at a temperature of a few million Kelvin. Jets of ions and electrons shoot out from there and scatter through space at the rate of 109 kg / s or 1036 particles per second.
The very hot gases that come from the solar wind are recognized by their content of hydrogen and helium ions. One part manages to enter the magnetosphere through the magnetopause, through a phenomenon called magnetic reconnection..
The solar wind constitutes a source of matter loss and angular momentum of the Sun, which is part of its evolution as a star..
The main source of plasma in the magnetosphere is the ionosphere. There the predominant gases are oxygen and hydrogen that come from the earth's atmosphere..
In the ionosphere they undergo an ionization process due to ultraviolet radiation and other high-energy radiation, mostly from the Sun..
The plasma of the ionosphere is colder than that of the solar wind, however a small fraction of its fast particles is capable of overcoming gravity and the magnetic field, as well as entering the magnetosphere..
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