An invisible shield, some 7,200 miles (11,600 km) above Earth, has been found blocking ‘killer electrons’ from bombarding our planet.
These electrons can whip around the planet at near-light speed and have been known to threaten astronauts, fry satellites and damage space systems.
If they hit Earth on a large scale, they could knock out power grids, radically change the planet’s climate and drive up rates of cancer.
But while scientists know this mysterious shield exists, they are baffled as to how it formed and how exactly it works.
‘Somewhat like the shields created by force fields on Star Trek that were used to repel alien weapons, we are seeing an invisible shield blocking these electrons,’ said Professor Daniel Baker from the University of Colorado Boulder.
The shield was discovered in the Van Allen radiation belts – two doughnut-shaped rings above Earth that are filled with high-energy electrons and protons.
Held in place by Earth’s magnetic field, the Van Allen radiation belts swell and shrink in response to incoming energy disturbances from the sun.
They were discovered in 1958 and are comprised of an inner and outer belt extending up to 25,000 miles (40,000km) above Earth’s surface.
Last year, Professor Baker led a team that used the twin Van Allen Probes launched in 2012 to discover a third, transient ‘storage ring’.
This ring is located between the inner and outer Van Allen radiation belts and seems to come and go with the intensity of space weather.
This ring appears to block the ultrafast electrons from breaching the shield and moving deeper towards Earth’s atmosphere.
‘It’s almost like these electrons are running into a glass wall in space,’ said Professor Baker.
‘It’s an extremely puzzling phenomenon.’
The team originally thought the highly charged electrons, which are looping around Earth at more than 100,000 miles per second, would slowly drift downward into the upper atmosphere.
But the impenetrable barrier seen by the twin Van Allen belt spacecraft stops the electrons before they get that far, said Professor Baker.
The group looked at a number of scenarios that could create and maintain such a barrier.
The team wondered if it might have to do with Earth’s magnetic field lines.
These lines trap and control protons and electrons, bouncing them between Earth’s poles like beads on a string.
They also looked at whether radio signals from human transmitters on Earth could be scattering the charged electrons at the barrier, preventing their downward motion.
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