spacetoday.net: "Invisible shield" blocks high-speed electrons above Earth

Posted: Sun, Nov 30, 2014, 11:37 AM ET (1637 GMT)
Van Allen Probes illustration (NASA)

Scientists said they have discovered a sharp feature in the Earth's magnetosphere that is blocking relativistic electrons from reaching the atmosphere. In a paper published in the latest issue of the journal Nature, scientists reported finding an "extremely sharp" boundary about 11,600 kilometers above the Earth where incoming electrons moving at close to the speed of light suddenly stopped. How that barrier is formed is unclear, although scientists speculate that it could be linked to low frequency electromagnetic waves created by the tenuous upper atmosphere that extends into the Van Allen belts. The discovery was made using data from NASA's Van Allen Probes mission.