![]() ![]() “But the impenetrable barrier seen by the twin Van Allen spacecraft stops the electrons before they get that far,” Prof Baker said. The scientists originally thought the highly charged electrons would slowly drift downward into the upper atmosphere and gradually be wiped out by interactions with air molecules. It’s an extremely puzzling phenomenon,” said Prof Baker, who is the first author of the paper published in the journal Nature. Somewhat like the shields created by force fields on Star Trek that were used to repel alien weapons, we are seeing an invisible shield blocking these electrons. “It’s almost like theses electrons are running into a glass wall in space. For the fastest, highest-energy electrons, this edge is a sharp boundary that, under normal circumstances, the electrons simply cannot penetrate. The new data from the Van Allen probes show that the inner edge of the outer belt (at roughly 11,500 km in altitude) is, in fact, highly pronounced. But generally the inner belt stretches from 650 to 9,650 km above Earth’s surface and the outer belt stretches from 13,500 to 58,000 km above the surface. In the decades since, researchers have learned that their size can change or they can merge, or even separate into three belts occasionally. The Van Allen belts themselves were detected in 1958 by the U.S. The barrier was discovered in the Van Allen radiation belts – a collection of charged particles, gathered in place by Earth’s magnetic field – using NASA’s Van Allen probes, launched in August 2012 to study the region. ![]() Image credit: NASA’s Scientific Visualization Studio. However, if realistically scaled for particle mass and energies, the spiral motion would not be visible at this distance so particle masses and size scales are adjusted to make them visible. Yellow particles represent negative-charged electrons, blue particles represent positive-charged ions. The radiation belt is sliced open, simultaneously revealing representative confined charged particles spiraling around the magnetic field structure. The radiation belts (rainbow-color) and plasmapause (blue-green surface) surround Earth, its structure largely determined by Earth’s dipole magnetic field (represented by cyan curved lines). In addition to the inner and outer radiation belts, the cooler plasma of the plasmasphere interacts so that it keeps out the higher-energy electrons from outside its boundary, called the plasmapause. Plasma interactions can generate sharply delineated regions in these belts. The near-Earth space environment is a complex interaction between the magnetic field of our planet, cool plasma moving up from its ionosphere, and hotter plasma coming in from the solar wind these interactions combine to maintain the radiation belts around Earth. ![]()
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