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Earth has a Plasma Shield

Category: Science & Technology
Posted: 03:06PM

On the surface of the Earth we are not exposed to much radiation, but surrounding the planet are belts of very high energy radiation, such as electrons traveling at nearly the speed of light. For years now we have observed at these ultrarelativistic electrons do not come to close to the Earth, but have not understood why. Using data from NASA's Van Allen Probes, researchers at MIT have devised an explanation that could be of great use for future satellites.

These ultrarelativistic electrons move so fast that they can complete an orbit of the Earth in just five minutes. With so much energy, they pose a serious risk to satellites and astronauts, but for conveniently they do not come within 11,000 Km of the Earth's surface. To explain this limit, the researchers looked at a few possibilities, including the Earth's magnetic field and ground-based radios. The magnetic field could not be the answer, because the limit is not affected by weak spots in it, and terrestrial radio waves would not affect the high energy electrons. What the researchers eventually determined was that the solution has to do with the plasmapheric hiss. This is a phenomenon of very low frequency electromagnetic waves in the Earth's upper atmosphere. The researchers determined that when the electrons encounter it, they are made to move parallel to the Earth's magnetic field, which causes them to collide with neutral gas atoms, which absorb them.

This explanations means there is a very firm barrier that will prevent any of these ultrarelativistic electrons from coming below 11,000 Km. Such information will be very important to future satellites, as it effectively gives them a safe zone where they will be free of this ionizing radiation, allowing for much longer lifespans.

Source: MIT

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