An invisible 'force field' reminisce of Star-Trek's deflector shields has been discovered 7,200 miles above Earth, protecting the planet from "killer electrons".

The so-called force field, discovered by astronomers working at the University of Colorado, is found in the Van Allen radiation belts - two doughnut shaped rings above Earth filled with high-energy electrons and protons.

In the CGI video above, the radiation belts (rainbow-colour) and plasmapause (blue-green surface) surround Earth. The yellow particles represent negative-charged electrons, whilst blue particles represent positive-charged ions. The cooler plasma of the plasmasphere (the plasmapause) interacts so that it keeps out the higher-energy electrons from outside its boundary.

The Van Allen radiation belts were first discovered in 1958, and found to be comprised of an inner and outer belt reaching up to 25,000 miles above Earth's surface. The belts swell and shrink in response to incoming energy disturbances from the Sun.

Video courtesy of Nasa