Modern Physics

Earth’s magnetosphere: characteristics, structure, gases

The Earth’s magnetosphere is the planet’s magnetic envelope against the current of charged particles that the Sun continually emits. It is caused by the interaction between your own magnetic field and the solar wind.

It is not a unique property of Earth, as there are many other planets in the solar system that have their own magnetic field, such as: Jupiter, Mercury, Neptune, Saturn or Uranus.

This flow 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 imparted an electrical charge to the particles. It consists mainly of free electrons and protons.

The solar corona emits these particles with so much energy that they can escape gravity in a continuous flow. It’s called the 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 surrounds the Earth’s magnetosphere.

The solar wind, which has a high electrical conductivity, is responsible for distorting the Earth’s magnetic field and compressing it on the side facing the Sun. This side is called the day side . On the opposite side, or on the night side , the field moves away from the Sun and its lines extend forming a kind of tail.


– Magnetic influence zones

The solar wind modifies the Earth’s magnetic field lines. If not for him, the lines would expand to infinity, like 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 noticeable.

2) Magnetofunda or magnetoenvolution, 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 magnetofundo is limited by two very important surfaces: the magnetopause and the shock front .

The magnetopause is the boundary surface of the magnetosphere, approximately 10 rays from Earth on the day side, but it can be compressed even further, especially when large amounts of mass are released from the solar corona.

On the other hand, the shock front or shock arc is the surface that separates the magnetofundo from the interplanetary zone. It is at this end that magnetic pressure begins to stop the particles in the solar wind.

– The interior of the magnetosphere

In the diagram in Figure 2, in the magnetosphere or cavity that contains the Earth’s magnetic field, distinct zones are distinguished:

– Plasmasphere

– plasma sheet

– Magnetoglue or magnetic glue

– neutral point

plasma sphere

The plasma sphere is an area formed by a plasma of particles from the ionosphere. There, they also stop particles coming directly from the solar corona that have managed to infiltrate.

They all form a plasma that is not as energetic as that of the solar wind.

This region starts 60 km above the Earth’s surface and extends to 3 or 4 times the radius of the Earth, including the ionosphere. The plasma sphere rotates on Earth’s side and partially overlaps the famous Van Allen radiation belts.

Magnetocola and plasma plate

The change in the direction of the earth’s field due to the solar wind gives rise to the magnetocola and also a confined area between the magnetic field lines with opposite directions: the plasma plate , also known as the current plate , of several thick earth rays.

Neutral point

Finally, the neutral point is a place where the strength of the magnetic force is completely canceled out. Figure 2 shows one of them, but there’s more.

Between the diurnal and nocturnal part of the magnetopause, there is a discontinuity, called the cusp , where the lines of magnetic force converge towards the poles.

It is the cause of the northern lights, as the particles in the solar wind spiral along the magnetic lines. Thus, they manage to reach the upper atmosphere of the poles, ionizing the air and forming plasmas that emit bright colored light and X-rays.


The magnetosphere contains appreciable amounts of plasma: an ionized gas of low density formed by positive ions and negative electrons, in proportions that make the whole almost neutral.

The density of the plasma is very variable and is between 1 to 4000 particles per cubic centimeter, depending on the area.

The gases that form the magnetosphere’s plasma come from two sources: the solar wind and the Earth’s ionosphere. These gases form a plasma in the magnetosphere formed by:

– Electrons

– Protons and 4% of [SEEM INCOMPLETE]

– Alpha particles (helium ions)

Complex electrical currents are created within these gases. The current intensity of the plasma in the magnetosphere is approximately 2 x 10 26 ions per second.

Likewise, it is an extremely dynamic structure. For example, within the plasma sphere, the plasma half-life is several days and its motion is mainly rotary.

On the other hand, in the outermost regions of the plasma sheet, the half-life is hours and its movement depends on the solar wind.

solar wind gases

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 fire from there and disperse through space at a rate of 10 9 kg / s or 10 36 particles per second.

The very hot gases from the solar wind are recognized by their hydrogen and helium ion content. A part manages to enter the magnetosphere through the magnetopause, through a phenomenon called magnetic reconnection.

The solar wind is a source of the Sun’s loss of matter and angular momentum, which is part of its evolution as a star.

Ionosphere gases

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, mainly from the sun.

The plasma of the ionosphere is cooler than that of the solar wind, however, a small fraction of fast-moving particles are able to overcome gravity and the magnetic field, in addition to entering the magnetosphere.

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