Interplanetary Environment >> Radiation Belts

Radiation Belts or Van Allen Belts

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.

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.

The figure shows the complex orbits of
the Van Allen belts in which the particles move.