innermagnetosphere

The inner magnetosphere is the portion of Earth’s magnetosphere closest to the planet, where the magnetic field remains largely dipolar and plasma populations co-rotate with Earth. It extends from the ionosphere outward to a few Earth radii and includes the plasmasphere, the inner radiation belt, and the inner portion of the ring current.

The plasmasphere is a torus of relatively cold, dense plasma that co-rotates with Earth. Its outer boundary, the plasmapause, moves inward or outward in response to geomagnetic activity. The inner radiation belt contains high-energy electrons and ions confined near Earth, typically within roughly 1.5 to 2.5 Earth radii. The inner ring current is carried by ions and electrons flowing westward and contributes to magnetic field perturbations during geomagnetic storms.

Dynamics in the inner magnetosphere are driven by solar wind energy input, substorms, and geomagnetic activity. Fresh particle populations can be injected from the plasma sheet and accelerated by wave-particle interactions, while losses occur through scattering into the atmosphere or loss to the magnetopause. These processes influence radiation belt intensities and the strength of the ring current, affecting near-Earth space weather.

Observationally, the inner magnetosphere is studied with Earth-orbiting and deep-space satellites, including missions such as the Van Allen Probes. It is of practical importance because energetic particles pose radiation hazards to satellites and astronauts and influence systems relied on for communications and navigation during space weather events.