The Van Allen Radiation Belts
Earth wears a belt. Actually, two belts. Surrounding Earth are two toroidal (doughnut shaped) radiation belts, one considered the outer and the other the inner belt. They were discovered in 1958 by astrophysicist James Van Allen, whose team at the University of Iowa was responsible for the instrumentation aboard the first U.S. science satellite, Explorer 1. Van Allen used data collected by Explorer 1 during its orbit of Earth, specifically a lower-than-expected cosmic ray count, to suggest the existence of a radiation belt around the planet
He was right. The Van Allen radiation belts are created by high-energy, electrically-charged particles (almost all protons and electrons) that originate from the sun (this is also known as cosmic radiation) and become trapped in the Earth's magnetic field. The belts are considered to be some of the most dangerous regions of space as we know it.