The NASA-produced video below helps explain what they learned when one of their twin Van Allen research probes passed through a shockwave from a Coronal Mass Ejection (an explosion of solar matter from the sun).

Scientists still have much to learn about the Van Allen radiation belts, which were first discovered in the 1950's. The belts are enormous, donut-shaped rings of charged particles that circle magnetized planets like Earth. They contain particularly dangerous forms of radiation, held in place by the magnetic field surrounding the planet, and swell and shrink in response to changing conditions in space. This activity may play a role in protecting the Earth's inner atmosphere from radiation, but it also poses a threat to astronauts and spacecraft that orbit within the belts.

Understanding how the belts work is becoming more important as the world becomes more dependent on satellite technology. That's why, in August 2012, NASA launched two Van Allen probes into Earth orbit.