Skip to main content

Dangerous Radiation belts around the Earth in a doughnut shape  

The radiation belts (also known as the van Allen belts) are toroidal regions encircling the Earth, in which very energetic (that is, very fast) particles are found. These particles are essentially trapped in the geomagnetic field. One can consider these particles to be a form of ionising radiation. As such, these particles constitute a real danger for humans and for spacecraft in orbit around the Earth.

The energetic particles in the radiation belts move along the Earth’s magnetic field lines. In the magnetosphere, which largely consists of low-energy ionized gas originating from Earth, the magnetic field of our planet traps high-energy charged particles emitted from the Sun.

Two Van Allen belts and their distance from earth (heigth)

These particles are located in two particular “doughnut-shaped” regions of the magnetosphere, better known as the Van Allen belts. The belts are named after the American physicist James Alfred Van Allen who discovered them with a Geiger counter onboard Explorer 1, the first American satellite, in 1958.

  • The inner belt is centered at a height between 300 and 1,000 kilometers above the Earth and reaches up to about 10,000 kilometers, consisting mainly of energetic protons with energies exceeding 100 MeV and, to a lesser degree, of ions and electrons.
  • The outer belt extends from an altitude of about 10,000-40,000 kilometers, comprising mainly high energy (0.1–10 MeV) electrons.

The energetic particles in the radiation belts move along Earth’s magnetic field lines. Electrons drift eastward around the Earth while ions drift westward. They bounce between the stronger magnetic fields in the northern and southern hemispheres and gyrate around the local magnetic field.

These three panels show how the relative locations of the outer boundary of the Earth's plasmasphere, the plasmapause, (shown in blue) and the van Allen belts (shown in red) change according to geomagnetic conditions. Credits ESA - C. Carreau
The figure shows the complex orbits of the Van Allen belts in which the particles move.
The figure shows the complex orbits of the Van Allen belts in which the particles move.