About the Author Slides from the Lecture Presidential Lecture 1992 - James A. Van Allen

Figure 5. A schematic diagram of the motion of an electrically charged par­ticle in the external magnetic field of the Earth. The particle gyrates around a line of magnetic force, os­cillates from one hemisphere to the other, and gradually drifts in longi­tude around the Earth within a toroidal-shaped region. Protons drift westward and electrons, eastward. The pictured particle is one of a huge number of such particles that consti­tute a radiation belt.


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