Alternate Definitions for Radiation Belts

Two belts of radiation that surround Earth, also known as the Van Allen Belts. These two concentric donut-shaped regions are filled with high-energy particles from the sun and Earth's ionosphere that gyrate, bounce and drift, sometimes shooting down into Earth's atmosphere, sometimes escaping out into space. The inner belt is fairly stable; however, the outer belt can swell and shrink over time, sometimes inflating so much that the belts appear as one.