Magnetized planets, like Earth, are encircled by zones of particle radiation known as the "Van Allen belts," in which high-energy charged particles spiral to and fro, trapped by the planet's magnetic field
Space Science Institute (SSI),Space Weather Center, Glossary of Space Weather-Related Terms, Colorado, USA 2011. http://www.spaceweathercenter.org/glossary/001/01. html, (Space Wthr - Amer) {860}