May 18, 2017, 3:12 pm
The influence of human activity extends far beyond the surface of Earth.
Observations with NASA’s Van Allen Probes have revealed the presence of a human-made ‘bubble’ around our planet, sometimes acting as a barrier against high-energy particles.
Scientists say the phenomenon is likely caused by the very low frequency (VLF) radio signals used to communicate with deep-ocean submarines, and could be affecting the way particles move through our near-space environment.
In a new study, researchers set out to investigate human-induced space weather, including the effects of chemical release experiments, the high-frequency wave heating of the ionosphere, and the interaction of VLF waves and the radiation belts.
This revealed a VLF bubble surrounding the planet, which could even be detected by spacecraft such as the Van Allen Probes, which orbit high above Earth’s surface.
According to the researchers, these signals are sent out by ground stations to submarines.
But, they don’t just extend below the ocean’s surface.
Instead, VLF signals are also traveling beyond Earth’s atmosphere and into space, where they interact with high energy particle raditation.
‘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,’ said Phil Erikson, assistant director at the MIT Haystack Observatory, Westford Massachusetts.
The researchers also found that the outer reaches of the bubble lines up ‘almost exactly’ with the inner edge of the Van Allen radiation belts.
These belts are regions within the magnetosphere where high-energy protons and electrons are trapped by Earth's magnetic field.
This lower limit is said to be the ‘impenetrable barrier’ – but, without the presence of the VLF transmissions, scientists suspect the boundary would sit much closer to earth.
Data now show that the inner extent of the Van Allen belts sits much farther away than it did in satellite observations from the 1960s.
According to NASA, these radio signals could one day be used to remove excess radiation from the near-Earth environment, and scientists are working to see if VLF transmissions can remove charged particles in the upper atmosphere during extreme space weather events.
‘By understanding more about how VLF transmission helps shape our space environment, we learn more about this complex region surrounding us,’ a NASA video on the discovery explains.
‘The more we know, the more situational awareness we have to protect our satellites from natural radiation in space.’