Two giant donuts of this plasma surround Earth, trapped within a region known as the Van Allen Radiation Belts. The belts lie close to Earth, sandwiched between satellites in geostationary orbit above and satellites in low Earth orbit (LEO) are generally below the belts. A new NASA mission called the Radiation Belt Storm Probes (RBSP), due to launch in August 2012, will improve our understanding of what makes plasma move in and out of these electrified belts wrapped around our planet.
"We discovered the radiation belts in observations from the very first spacecraft, Explorer 1, in 1958" says David Sibeck, a space scientist at NASA's Goddard Space Flight Center in Greenbelt, Md., and the mission scientist for RBSP. "Characterizing these belts filled with dangerous particles was a great success of the early space age, but those observations led to as many questions as answers. These are fascinating science questions, but also practical questions, since we need to protect satellites from the radiation in the belts."
The inner radiation belt stays largely stable, but the number of particles in the outer one can swell 100 times or more, easily encompassing a horde of communications satellites and research instruments orbiting Earth. Figuring out what drives these changes in the belts, requires understanding what drives the plasma.