The existence of a slightly dipolar field and of a dense atmosphere leads to the formation of a well-developed magnetosphere around the Earth. The lines of force of themagnetic field are distorted by the solar wind (coming from the sun at the left of the figure). The interaction between the solar wind and magnetosphere is very dynamic due to permanent variations in the solar wind.
Various different regions may be distinguished :
- The solar wind
- The magnetospheric bow shock accompanying the Earth in its supersonic movement with respect to the solar wind : it is located approximately 12 to 14 Earth radii towards the sun.
- The magnetosheath, mainly consisting of solar wind particles, in which the magnetic field varies widely in both intensity and direction.
- The magnetopause, the true limit of the influence of the Earth's magnetic field: it is located 10 Earth radii towards the sun and has a long plasma tail on the opposite side. In the equatorial part of this tail is the plasma layer, which is relatively dense compared to other areas around it at a higher latitude.
- An unstable trapping region in which charged particles follow the lines of force of the magnetic field, but whose exchanges with adjacent regions are numerous, especially around "polar cusps" through which solar wind particles are able to penetrate the internal magnetosphere.
- A stable trapping region called Van Allen areas, extending as far as 5 Earth radii in equatorial regions.
- The plasmasphere, a plasma region coming mainly from the ionosphere, rotating with the Earth.
- The auroral lines of force, which are located at a high altitude between the plasmasphere and the polar cusp.