The Van Allen radiation belts in in the Earth's upper atmosphere, two doughnut-shaped rings of highly charged particles, were discovered in 1958. The Van Allen radiation belts consist of an inner ring of high-energy electrons and energetic positive ions, and an outer ring of high-energy electrons.
But then in February of this year, a team of scientists writing in Science reported a previously unknown third radiation ring, which circled the Earth between the inner and outer rings in September 2012 and then almost completely disappeared.
How did this temporary radiation belt appear and dissipate?