Third radiation belt around earth discovered

National Aeronautics and Space Administration scientists claim to have discovered a third radiation belt around the earth, which may lead to a revision of a more than 50-year-old theory about the planet's radiation zones.

The Van Allen radiation belts surrounding the earth were thought to be just two giant swaths of radiation, first discovered in 1958, the American space agency said.

NASA launched twin Van Allen Probes on August 30, 2012 to create a detailed map of the region and catalogue a variety of energies and particles in these radiation belts.

Just three days after launch, scientists asked that the Relativistic Electron Proton Telescope be turned on early in order that its observations would overlap with another mission called Solar, Anomalous, and Magnetospheric Particle Explorer, that was soon going to de-orbit and re-enter earth's atmosphere.

Shortly before REPT turned on, solar activity on the sun had sent energy towards Earth that caused the radiation belts to swell. The REPT instrument made observations of these new particles trapped in the belts, recording their high energies, and the belts' increased size.

The particles settled into a new configuration, showing an extra, third belt extending out into space. "By the fifth day REPT was on, we could plot out our observations and watch the formation of a third radiation belt," said Shri Kanekal, the deputy mission scientist for the Van Allen Probes at NASA's Goddard Space Flight Center in Greenbelt and a co-author of the study.

"We started wondering if there was something wrong with our instruments. We checked everything, but there was nothing wrong with them. The third belt persisted beautifully, day after day, week after week, for four weeks," Kanekal said in a statement.

Subsequent missions have observed parts of the belts, but what causes such dynamic variation in the belts has remained something of a mystery. The study was published in the journal Science.