In 1958 a geiger counter on the the Explorer 1 satelitte detected intense
particle radiation in particular regions surrounding the earth.
These measurements led to the discovery of the earth's magnetosphere.
These belts lie within the plasmosphere and where named after their
discoverer, Van Allen.
Two distinct donut shaped belts were discovered that coincided with the
inner magnetic field lines of the earth. The inner belt was found to be
made up of high energy protons and the outer belt conatained high energy
The inner belt of protons is produced when cosmic rays strike particles in the
upper atmosphere. The outer belt is populated with electrons produced by
cosmic rays and magnetospheric accelleration processes.
The charged particles contained in the Van allen belts remain trapped along field lines of the earth. The particles bounce and drift in a spiral motion along the earth's magnetic field lines. As the particles approach the converging field lines near the poles they are reflected back towards the opposite pole.