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Whoops, Humans Made a Space Barrier Around Earth

Popular Mechanics logo Popular Mechanics 12/16/2020 Caroline Delbert
Earth is surrounded by a radio field caused by very low-frequency waves. This field pushes away the Van Allen radiation belts. © NASA Earth is surrounded by a radio field caused by very low-frequency waves. This field pushes away the Van Allen radiation belts.
  • Earth is surrounded by a radio field caused by very low-frequency waves.
  • This field pushes away the Van Allen Belts, a radiation swim-floaty that surrounds Earth's middle.
  • Van Allen radiation hinders and complicates spaceflight, magnetic instruments, and more.

Forget the Kármán line—there’s a human-made space barrier to wonder about, first observed by NASA in 2017. The mysterious zone of anthropogenic space weather is caused by specific kinds of radio waves that we’ve been blasting into the atmosphere for decades, but experts say the expanding band actually helps protect humankind from dangerous space radiation.

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ScienceAlert reports that NASA first observed this belt in 2012. The agency sends probes to explore different parts of our solar system, including the Van Allen Belts: a huge, torus-shaped area of radiation that surrounds Earth. The donut shape follows the equator, leaving the North and South Poles free.

diagram, schematic: A cross section of Van Allen radiation belts. © NASA/Public Domain A cross section of Van Allen radiation belts.

The Van Allen Belts are related to and affected by the magnetosphere induced by the nonstop bombardment of the sun’s radiation. They affect benign-seeming magnetic effects like the Northern Lights, as well as more destructive ones like magnetic storms.

People planning spaceflight through areas affected by the Van Allen Belts, for example, must develop radiation shielding to protect crew as well as equipment—and most spacecraft launch from as near to the equator as possible, right in the Van Allen zone.

So, what’s our new protective barrier? The same probes that launched in 2012 to help us understand the Belts better in the first place detected this phenomenon, and in 2017, the probes gave us the first evidence of the radio-wave barrier emanating from Earth. ScienceAlert explains:

“A certain type of transmission, called very low frequency (VLF) radio communications, have become far more common now than in the 60s, and the team at NASA confirmed that they can influence how and where certain particles in space move about.”

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Why is this? Well, the very low frequency (VLF) waves are exactly right to cancel out and repel the radiative advances of the Van Allen Belts as a matter of total coincidence. In fact, NASA initially considered this a true coincidence, saying that a radio wave area happened to match exactly with the edge of the Van Allen Belts. But in 2017, the agency published findings revealing that one has caused the other after all.

Typically, services like the military have dibs on very low frequencies. These were the first frequencies to be discovered and used for broadcasting, but successive discoveries pushed private and recreational users further up the spectrum. At the very lowest point is the simplest broadcast, things like Morse code, where only binary values need to be received. After that, VLF used by military equipment, for example, occupies a chunk of wavelengths.

From there, AM is still pretty low, and FM is farther up. Some “regular” bandwidths of civilian-type radio are off limits because they’re used for more traditional radio communications by people like pilots and ship captains for different purposes. Any physical communication like this must be negotiated—remember the government has objected to some 5G ideas because of the conflict with GPS satellite signals.

Isn’t it interesting that VLF blankets the Earth without interfering with literally any other radio signal, for example, or the many other kinds of waves that flow around us all the time, but makes it into space far enough to push away harmful radiation?

This means that, for example, space programs could develop VLF technology to punch holes for spacecraft to travel through. As always, truth is stranger than fiction.

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