Wednesday, May 17, 2017

Radio communications have surprising influence on Earth's near-space environment

Humans have a measurable effect on Earth's near-space environment, new research shows.

Very low frequency radio communications interact with and influence particles in space. These interactions can sometimes yield a protective barrier, blocking incoming high energy particles.

The barrier has been detected by NASA's Van Allen Probes, robotic spacecraft tasked with surveying Earth's Van Allen radiation belts.

"A number of experiments and observations have figured out that, under the right conditions, radio communications signals in the VLF frequency range can in fact affect the properties of the high-energy radiation environment around the Earth," Phil Erickson, assistant director at the MIT Haystack Observatory, said in a news release.

VLF radio communications feature frequencies between 3 and 30 kilohertz. VLF's limited bandwidth isn't suitable for audio transmission. It's typically used for the long-distance transmission of coded signals by the military.

VLF radiation enables communication between bases and submarines, but the waves bounce out beyond the atmosphere, too.

While analyzing data from the Van Allen Probes, scientists realized the VLF bubble often corresponds with the lower limit of the Earth's radiation belts, streams of charged particles held in place by Earth's magnetic field.

Historical observations show the lower limits of the Van Allen radiation belts are farther from Earth today than they were in the 1960s, when VLF communications were less common. The findings -- detailed in the journal Space Science Reviews -- suggest VLF waves are pushing the Van Allen Belts outward.

Researchers are testing whether VLF radiation could be used to rid the upper atmosphere of excess radiation. Space weather can flood the upper atmosphere with charged particles, interrupting important communications systems.

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