- noun a region surrounding the earth, extending from about 500 to several thousand kilometres above the surface, in which charged particles are controlled by the Earth’s magnetic field
- The area of magnetic influence of the Earth in space. The Earth’s magnetosphere is a volume stretching a short and variable distance towards the Sun, meeting its magnetic influence at the magnetopause, but running out deep into the solar system behind the Earth within the magnetosheath. The Earth is not completely isolated from the Sun’s magnetism by its own magnetic field. Instead, charged particles penetrate it in significant numbers, supplying the Van Allen belts with material and causing effects like the Aurora. The term is also applied by analogy to the space around other planets with significant magnetic fields.
- The region in space where the earth's magnetic field exerts a significant influence. It starts within the ionosphere, and extends to about 10 or so earth radii, although this value may be much higher on the side opposite the sun. The magnetosphere is distorted into a teardrop shape by the solar wind. The term may also refer to such a region of another celestial body.