Van Allen Radiation Belts
Keywords:atmosphere, deflections, Geiger-Muller, geimagnetic, azimuthal
This article is about the Van Allen radiation belts.
The low energy charged particles in the upper atmosphere due to primary radiation from outer space, the secondary particles produced by interaction of primary rays with nuclei, and the lower energy particles emitted by the sun cannot land on the Earth due to deflections in the geomagnetic field. It was discovered in 1958, by sending Geiger-Muller counters abroad Explorer I and III, the existence of an intense radiation belt surrounding the earth, essentially symmetrically, several thousand kilometres above its surface. It was observed that low energy charged particles are permanently trapped in the radiation belt and spiral back and forth between definite geomagnetic latitudes in the two hemispheres. Two such doughnut-shaped radiation belts were discovered and are called Van Allen radiation belts after is discoverer Van Allen. The inner belt, produced by low energy protons is situated at an altitude of about 3200 km. The outer belt is due to trapping of electrons from the sun and low energy protons and is located at an altitude of 10,000 to 70,000 km round the earth. Both the belts are observed at all azimuthal angles about the geimagnetic axis
Modern atomic and nuclear physics- AB Gupta