From Popular Science
When the Navy wants to send a message to an underwater submarine, it sometimes uses very low frequency (VLF) radio waves. These long wavelengths, beamed from large towers on the ground, are unique in their ability to travel through salty water. But some end up in space instead. There, according to a new report, they may be forming a protective bubble around Earth’s atmosphere.Read more: http://www.popsci.com/radio-wave-shield-space-weatherThe discovery comes from the Van Allen Probes—two spacecraft, launched in 2012, that patrol the radiation belts surrounding Earth. The Van Allen radiation belts are zones where charged particles streaming from the sun get stuck in Earth’s magnetic field. These high energy protons and electrons can destroy a satellite’s electronics, which is a constant concern because the belts don’t always stay in one place.
“The conventional wisdom is that the inner edge of the outer belt kind of moves in and out as the atmosphere—especially ionosphere and plasmasphere—grows and shrinks,” says Phil Erickson, a space plasma physicist at MIT. But observations from the Van Allen Probes showed that radio waves may also play a role in determining the location of the radiation belts.
During an intense geomagnetic storm in 2015, a large solar storm knocked back the plasmasphere, but surprisingly the outer Van Allen belt didn’t come any closer to Earth. “The plasma retracted but the belt didn’t follow,” says Erickson. But he and his colleagues noticed something else: “The edge of where these very powerful radio signals stop is the same place where the electrons stop coming in.”In addition, data from the 1960s suggests that the belt’s inner boundary was much closer to Earth back when VLF transmissions were less common. The team thinks that, nowadays, when electrons shooting out from a solar storm approach Earth, VLF waves deflect them, knocking them off their trajectory and pushing them into the atmosphere, where they get lost.
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