Researchers say a donut-shaped shield protects Earth from streams of radiation streaming through space. Photo by Andy Kale/University of Alberta.
BOSTON, Nov. 26 (UPI) -- Electrons in the Van Allen radiation belt stream through space at close to the speed of light, but thanks to a seemingly invisible donut-shaped shield surrounding Earth, they're never able to get closer than about 7,200 miles from the surface.
What exactly prevents these high-energy particles from penetrating further? Researchers at MIT and the University of Colorado have identified a phenomenon called "plasmaspheric hiss" as responsible for defending Earth from the harmful radiation.
"It's almost like theses electrons are running into a glass wall in space," Daniel Baker, director of CU-Boulder's Laboratory for Atmospheric and Space Physics, explained in a press release. "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 an extremely puzzling phenomenon."
Scientists first hypothesized that air molecules or the Earth's magnetic field worked as the Earth's main defense against these electron streams. But the strict boundaries of the newly discovered shield didn't correspond with these features.
Instead, researchers say plasmaspheric hiss -- electromagnetic waves found throughout the dense plasma region that encircles Earth -- slowly rotates the paths of the electrons, slowing their descent into Earth's upper atmosphere, where they ultimately collide with neutral atoms and are nullified. If one were to listen plasmaspheric hiss on the radio, it would sound like static or white noise.
"It's a very unusual, extraordinary, and pronounced phenomenon," John Foster, associate director of MIT's Haystack Observatory, said in a press release. "What this tells us is if you parked a satellite or an orbiting space station with humans just inside this impenetrable barrier, you would expect them to have much longer lifetimes. That's a good thing to know."
The research is detailed in the latest issue of the journal Nature.