Published in Physics World, 7 May 2009
If it weren’t there, astronauts and satellites might well be showered with electrons at lethal energies. It’s “plasmaspheric hiss” — a natural radio wave that lies in just the right place outside the Earth to deflect high-energy electrons out of space and safely into the atmosphere. Since its discovery more than 40 years ago no–one has been sure of its origin, but now researchers from the US, Sweden and France claim to have the answer.
Having analyzed data from NASA’s THEMIS mission, Jacob Bortnik of the University of California at Los Angeles and colleagues think plasmaspheric hiss is generated by secondary “chorus” emission of electromagnetic waves from unstable electrons farther out. “I personally thought we would not be able to find such an observation,” says Bortnik. “Turns out I was pleasantly surprised.” […]
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