NASA's first satellite, launched in 1958, discovered two giant swaths of radiation encircling Earth. Five decades later, scientists are still trying to unlock the mysteries of these phenomena known as the Van Allen Belts. As solar wind and cosmic rays carry fast-moving, highly energized particles past Earth, scientists think some of these particles become trapped by the planet's magnetic field. The resulting belts, one inner and one outer, can swell or shrink in size in response to incoming particles from Earth's upper atmosphere and changes in the solar wind. But sometimes the belts don't change when scientists expect them to. New NASA spacecraft scheduled to launch in August 2012 seek to determine what kinds of solar outbursts and other space weather cause specific changes in the radiation belts—answering some of the questions first raised decades ago. The visualization shows the belts responding to a strong, steady burst of material and energy from the sun.
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NASA's Goddard Space Flight Center
Historic image of Van Allen Belts courtesy of NASA Langley Research Center