Van Allen radiation belt
The Van Allen radiation belt is a zone of energetic charged particles, most of which originate from the solar wind, that are captured by and held around a planet by that planet’s magnetosphere. Earth has two such belts, and sometimes others may be temporarily created. The belts are named after James Van Allen, who published an article describing the belts in 1958.
Earth’s two main belts extend from an altitude of about 640 to 58,000 km (400 to 36,040 mi) above the surface, in which region radiation levels vary. The belts are in the inner region of Earth’s magnetic field. They trap energetic electrons and protons. Other nuclei, such as alpha particles, are less prevalent. Most of the particles that form the belts are thought to come from the solar wind while others arrive as cosmic rays. By trapping the solar wind, the magnetic field deflects those energetic particles and protects the atmosphere from destruction.
The belts endanger satellites, which must have their sensitive components protected with adequate shielding if they spend significant time near that zone. Apollo astronauts going through the Van Allen belts received a very low and harmless dose of radiation.
In 2013, the Van Allen Probes detected a transient, third radiation belt, which persisted for four weeks.
The Van Allen belts are donut-shaped zones of energetic charged particles trapped by Earth's magnetosphere, primarily composed of protons and electrons originating from solar wind and cosmic rays. Discovered by James Van Allen in 1958, these belts pose radiation hazards to spacecraft and astronauts, requiring shielding and rapid transit through them during space missions. During intense solar storms, the belts can expand and become more dangerous, impacting satellites and even Earth’s power grids.
- Inner Belt: Located closer to Earth, it is primarily composed of protons resulting from cosmic rays interacting with the atmosphere.
- Outer Belt: Situated farther from Earth, this belt is more variable and contains less energetic protons, electrons, and other ions.
- Temporary Third Belt: Sometimes, especially during solar storms, a third, outermost belt can briefly form.
- Earth’s Magnetic Field: The belts are a direct consequence of Earth’s magnetic field, which traps and holds the charged particles.
- Solar Wind and Cosmic Rays: The primary source of particles in the Van Allen belts is the solar wind, a continuous stream of charged particles from the Sun, as well as high-energy cosmic rays.
- Radiation Exposure: The energetic particles in the belts can damage sensitive electronics on spacecraft and pose significant radiation risks to astronauts.
- Solar Storms: During solar storms, the belts can swell dramatically, increasing radiation levels and potentially disrupting satellites, GPS systems, and communication.
- Spacecraft Design: Spacecraft, like NASA’s Van Allen Probes, are designed with hardened components to withstand the harsh environment of the belts.