NASA boffins in charge of the agency's Van Allen Belt mission have recorded audio-frequency noise made by energetic electrons emitting what's known as “whistler waves”.
NASA Goddard says the waves shape the near-Earth space environment and also characterise different types of plasma, making them worthy of our curiosity.
So why publish recordings of them? Because it's cool, of course.
There's the plasmasphere around Earth, relatively dense and cold, which produces different frequencies to hotter, less dense waves in the Van Allen Belts. Those waves (going by the snappy name Enhanced EMIC – Electromagnetic Ion Cyclotron – waves) hiss.
Different regions of the magnetosphere create different electron whistler waves. Image: NASA
Further out, “chorus waves” chirp. Goddard explains they are “created when electrons are pushed towards the night side of Earth — which in some cases, may be caused by magnetic reconnection, a dynamic explosion of tangled magnetic field lines on the dark side of Earth.
“When these low energy electrons hit the plasma, they interact with particles in the plasma, imparting their energy and creating a unique rising tone”.
The also-complex whistler waves are sure to land in the Foley kit-bags of sci-fi sound effects people for years.
The recordings were captured by the EMFISIS (Electric and Magnetic Field Instrument Suite and Integrated Science) instrument aboard NASA’s Van Allen Probes as it passed around Earth. ®