A cutaway model of the radiation belts with the 2 RBSP satellites flying through them. The radiation belts are two donut-shaped regions encircling Earth, where high-energy particles, mostly electrons and ions, are trapped by Earth’s magnetic field. This radiation is a kind of “weather” in space, analogous to weather on Earth, and can affect the performance and reliability of our technologies, and pose a threat to astronauts and spacecraft.
The inner belt extends from about 1000 to 8000 miles above Earth’s equator. The outer belt extends from about 12,000 to 25,000 miles. This graphic also shows other satellites near the region of trapped radiation. Credit: NASA
The Van Allen Probes, two nearly identical spacecraft, launched in August 2012 and with only six months in operation, they may well be rewriting science textbooks. The probes study the Van Allen belts, gigantic radiation belts surrounding Earth, which can swell dramatically in response to incoming energy from the sun, engulfing satellites and spacecraft and creating potential threats to manned space flight.
James Van Allen discovered the radiation belts during the 1958 launch of the first successful U.S. satellite. Subsequent missions have observed parts of the belts, but what causes the dynamic variation in the region has remained something of a mystery.