Two rings of highly energetic charged particles encircle the earth, trapped in its magnetic field. The inner ring, made up mostly of protons, hovers about 500 miles above our heads. The outer ring is mostly made up of electrons.
These radiation belts are named for astrophysicist James Van Allen, who first discovered them. Though the Van Allen belts are invisible to the naked eye, an instrument called PAMELA gives physicists an idea what they would look like.
The Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics, or PAMELA, telescope was launched in June 2006 from Kazakhstan in part to study the radiation belts. Its goals are to search for dark matter, baryon asymmetry, and the source of cosmic rays. Marco Casolino, a researcher at the National Institute of Nuclear Physics in Rome, described the instrument in a talk at the Physics in Collision conference in Kobe, Japan, this week.
To illustrate its capabilities, he showed the following fascinating animation:
The video gives a tour of the Van Allen belts, as measured with PAMELA spectrometer on board Russian satellite Resurs-DK1. Measurements are between 600 and 370 km and are shown to scale.