This picture shows that there are three small regions in which the particles are trapped. These regions are the plasmaspheres.
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T.S. Huang
The Plasmaspheres of Neptune
Neptune has three tiny plasmaspheres. The rings of Neptune sweep away much of the particles in the area.
Particles enter the plasmasphere from the atmosphere as well as the magnetotail. Mathematical theory suggests that particles leave the plasmasphere by being swept directly into the atmosphere.
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