innerbelt

Inner belt, or inner Van Allen radiation belt, is a torus-shaped region of space around the Earth in which charged particles are trapped by the planet's magnetic field. It forms one of the two main components of the Earth's radiation belts and extends from roughly 1,000 to 12,000 kilometers above the Earth's surface (about 600 to 7,500 miles). The belt is dominated by high-energy protons, with electrons present as well, though the proton population is the defining feature. Particles originate from solar particle events and cosmic rays that become trapped by the geomagnetic field and accumulate in the belt over time.

The inner belt is relatively stable compared with the outer belt, though its intensity can vary with solar activity and geomagnetic conditions. It plays a key role in radiation exposure for satellites and spacecraft operating within or passing through its region, and poses risks for astronauts during certain mission profiles. The belts are bordered by the outer belt and the atmosphere, with interactions between waves and particles contributing to gradual loss of particles into the atmosphere.

Discovery and research: The Van Allen radiation belts were identified in 1958 from data collected during the Explorer 1 mission and subsequent satellites, and were named after James Van Allen, who led the experiment team. Ongoing research uses satellite measurements and ground-based observations to understand particle acceleration, transport, and loss processes within the magnetosphere. Related topics include the magnetosphere and the broader radiation-belt system.