May 19, 2017
Space weather can have a big effect on human society. Sometimes
human society returns the favor...
A new study entitled
"Anthropogenic Space Weather" just published in
Reviews outlines how human activity shapes the space around our
A prime example:
radio transmissions form a bubble in space protecting us from
Co-author Phil Erickson of MIT's Haystack Observatory
"As Van Allen
discovered in the 1950s and 1960s, there are two radiation belts
surrounding Earth with a 'slot' between them.
Our research is
focused on the the outer radiation belt, which contains
electrons with energies of a million or more electron-volts.
These 'killer electrons' have the potential to damage
spacecraft, even causing permanent failures."
During strong geomagnetic
storms, the outer radiation belt expands, causing the killer
electrons to approach Earth.
Probes, a pair of spacecraft sent to explore the radiation belts,
found that something was stopping the particles from getting too
"The penetration of
the outer belt stopped right at the same place as the edge of
VLF strong transmissions from humans on the ground," says
transmissions penetrate seawater, so we use them to communicate
They also propagate
upward along Earth's magnetic field lines, forming a 'bubble' of
VLF waves that reaches out to about 2.8 Earth-radii - the same
spot where the ultra-relativistic electrons seem to stop."
VLF radio waves clear the area of killer electrons,
"via a wave-particle
gyro-resonance," says Erickson.
"Essentially, they are just the
right frequency to scatter the particles into our atmosphere
where their energy is safely absorbed."
"Because powerful VLF transmitters have been operating since
before the dawn of the Space Age, it is possible that we have
never observed the radiation belts in their pristine,
unperturbed state," notes the team, which includes John Foster,
a colleague of Erickson at MIT and a key leader of this
research, along with Dan Baker at the University of Colorado
effects on space weather include,
artificial radiation belts created
by nuclear tests
high-frequency wave heating of the ionosphere
cavities in Earth's magnetotail formed by