There’s hardly anything on Earth that has escaped human influence—from the oceans to the atmosphere. But a new study suggests that human activity is also influencing the space around our planet; this is on top of the space junk already swirling around out there. Very Low Frequency (VLF) broadcasts have created a planetary cocoon, shielding the planet from high energy particle radiation, according to a NASA press release.
As David Grossman at Popular Mechanics reports, VLF radio requires a massive antenna for detection—so they're only used for special purposes. One common use is for submarine communication, which works due to the penetrative capacity of the lengthy VLF waves. But they can also travel out into space. There, the signals interact with charged particles, changing their movement.
But the changes might not all be bad. As Marina Koren writes for The Atlantic, "The bubble forms a protective barrier around Earth, shielding the planet from potentially dangerous space weather, like solar flares and other ejections from the sun." This ephemeral bubble adds to the already protective magnetosphere, encompassing our planet. Researchers report the find this week in the journal Space Science Review.
The discovery was made using the Van Allen Probes, spacecraft launched in 2012 to monitor the bands of charged particles surrounding the Earth. The data from these probes suggest that the outer edge of the VLF transmission corresponds with a layer of charged particles at the inner edge of the Van Allen Belts. But according to satellite data, before VLF signals went into wider use in the 1960s, the Van Allen Belts stretched closer to the Earth. The researchers believe the VLF signals may be keeping the Belts from creeping closer.
But the VLF signal is not the only human activity affecting space. The study also examines other anthropogenic impacts on space weather. According to a press release, between 1958 and 1962 the U.S. and the U.S.S.R. conducted high altitude nuclear detonations. Those blasts, which were between 16 and 250 miles above the surface of the earth, mimicked some of the effects caused by solar wind, including bombarding the earth with high-energy particles, distorting the earth’s magnetic field and creating temporary radiation belts. One test even created an artificial aurora. The researchers hope to figure out how these blasts created or disrupted space weather.
“The tests were a human-generated and extreme example of some of the space weather effects frequently caused by the sun,” says Phil Erickson, assistant director at the MIT Haystack Observatory and an author on the study, in the press release. “If we understand what happened in the somewhat controlled and extreme event that was caused by one of these human-made events, we can more easily understand the natural variation in the near-space environment.”
But it's not all bad news. Researchers eventually hope to investigate new ways to use VLF signals to influence space weather to further protect the Earth from bombardment with charged particles during solar storms.