Likewise, the Van Allen belt is a zone of radiation. Typically of the ionizing kind, ie plasma, there is no defined net charge at the belt, it is magnetic interaction between the Earth's own weakening magnetic fields and both cosmic and solar particles. The earth is not a dipole, it has a net negative charge, the sun has a net positive charge, thus the sun and earth are electromagnetically coupled. Furthermore, the sun's atmosphere encompasses the entire solar system, thus termed 'heliosphere'.