"Raise shields!" may be a familiar defensive order given in the Star Trek Universe, but according to space scientists in our Universe, Planet Earth has its own built-in invisible shield that buffers "killer electrons" from orbital altitudes.
High energy particles, including electrons and protons, are known to speed around our planet at relativistic velocities - the high-energy electrons have been clocked traveling at a breakneck speed of 100,000 miles per second. These particles, which are held in two defined ‘doughnuts' above the Earth's atmosphere, are known to cause damage to satellites and also pose a risk to astronauts venturing beyond Earth orbit.
NEWS: Space Radiation Probes Make ‘Shock' Discovery
Discovered in 1958 by James Van Allen and his University of Iowa team, these famous Van Allen Belts were found to comprise of an inner belt and outer belt, extending 25,000 miles above the Earth's atmosphere.
In 2013, Daniel Baker of the University of Colorado, Boulder, used data from NASA's Van Allen probes to discover a third "storage ring" between the classical inner and outer belts that appeared and disappeared with the waxing and waning of space weather. The twin Van Allen satellites continue to orbit the Earth, zooming in and out of the radiation belts, giving us an unprecedented view of this dynamic and fascinating region.
Now, in a new study published in the Nov. 27 issue of the journal Nature, Baker and his collaborators have discovered an oddity at the inner edge of these belts: There's an invisible barrier blocking the high-energy electrons from making contact with our atmosphere.
"It's almost like theses electrons are running into a glass wall in space," said Baker in a UC press release. "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. It's an extremely puzzling phenomenon."
NEWS: Probes Launched Into Earth's Radiation Zone
As the Van Allen Belts are sandwiched between the magnetic layers of the Earth's magnetosphere, Baker's team assumed that it must be a magnetic barrier that is acting like a shield. But, bizarrely, that doesn't appear to be the case. Also, the researchers looked at radio waves generated by human sources; perhaps these transmissions are creating an electron scattering layer that forms a boundary? But that hypothesis didn't fit with the observations either.
"Nature abhors strong gradients and generally finds ways to smooth them out, so we would expect some of the relativistic electrons to move inward and some outward," said Baker. "It's not obvious how the slow, gradual processes that should be involved in motion of these particles can conspire to create such a sharp, persistent boundary at this location in space."
Now the researchers are focused on a cold cloud of electrically charged gas that is known to surround Earth, starting at an altitude of 600 miles. This cloud, known as the plasmasphere, extends thousands of miles into the Van Allen Belts and may have a dramatic interaction with the high-energy particles, thereby blocking them from dropping close to our atmosphere. High-energy electrons are stopped in their tracks at an "extremely sharp" boundary approximately 7,200 miles in altitude.
ANALYSIS: Can We Hack Space to Reduce Spacecraft Damage?
In short, this plasmasphere could be our planet's Star Trek shields.
"It's like looking at the phenomenon with new eyes, with a new set of instrumentation, which give us the detail to say, ‘Yes, there is this hard, fast boundary,'" added John Foster, of MIT's Haystack Observatory and a study co-author.
As yet, the researchers are not sure what mechanism is driving this interaction between the plasmasphere and high-energy electrons, though they suspect that low-frequency electromagnetic waves traveling through the plasmasphere may be scattering the electrons, creating a plasmaspheric ‘hiss.' More research is needed before this mechanism can be identified as what is driving Earth's "killer electron" shield, however, a challenge that is currently being met by the Van Allen probes.
Source: UC Boulder