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NASA discovers particle accelerator in Earth’s Van Allen Radiation Belts

How much damage can some roving electrons cause to a space satellite? Quite a lot, actually: Super-charged electrons running at high speeds through Earth’s radiation belt have actually been causing many satellites to meet untimely mission failures. And a recent study has identified the electrons’ power source within electromagnetic waves that encircle our planet.

The researchers, who published a paper on their findings this week in Science, relied on data collected by NASA’s two Van Allen space probes. NASA launched the Van Allen probes in August 2012 to discern the effects of the sun’s radiation on Earth and its surrounding space by studying the Van Allen belt, the series of massive rings of these charged electrons that encircle Earth.

Geoffrey Reeves, the Science paper’s lead author, likens the phenomenon to a tetherball, the magnetic field construed as the pole. The electromagnetic waves hit the tetherball—i.e., the electrons—and the electrons circle around the magnetic field in repeated loops. And with each rotation, the electrons gain more and more momentum.

Once they acquire enough acceleration, these electrons can reach speeds as high as 99% of the speed of light, according to Reeves. He said that they are the fastest objects our planet produces. As those speeds, they are capable of crashing through the satellite’s skin and piercing its electrical systems. Such collisions result in considerable damage to the satellite, sometimes severe enough to put the satellite permanently out of commission. They can also harm human astronauts, if those astronauts remain exposed to them for sustained lengths of time.

Researchers had previously hypothesized that the electrons originated from somewhere beyond Earth, but the Van Allen mission data indicate that this is not so. The Earth’s own magnetic fields gives rise to these electron rings. The U.S. astronomer James Van Allen discovered the belt in 1958, and later space missions identified two distinct layers, or “rings,” composing it.

Satellite data earlier this year indicated a third ring, although that ring subsequently vanished. The radiation belt, like many atmospheric phenomena closer to Earth’s surface, fluctuates throughout the year.

Reeves intends to follow up with further investigations into the precise electromagnetic waves that give rise to specific ranges of electron acceleration. He and other NASA colleagues hope to use these findings to develop better monitoring systems to guard against them and better on-board protections to minimize damage to a satellite in the event of an electron bombardment.