Van Allen radiation belts have been found to contain a nearly impenetrable barrier that prevents the fastest, most energetic electrons from reaching Earth.
The Van Allen belts are a collection of charged particles, gathered in place by Earth’s magnetic field. They can wax and wane in response to incoming energy from the Sun, sometimes swelling up enough to expose satellites in low-Earth orbit to damaging radiation. The discovery of the drain that acts as a barrier within the belts was made using NASA's Van Allen Probes, launched in August 2012 to study the region. A paper on these results appeared in the November 27, 2014, issue of Nature magazine.
Dan Baker, a space scientist at the University of Colorado in Boulder and first author of the newly released paper said this barrier for the ultra-fast electrons is a remarkable feature of the belts. "We're able to study it for the first time, because we never had such accurate measurements of these high-energy electrons before."
