It sounds like the call of an extraterrestrial bird species, but the recording featured in the video up top (and the player, down below) is actually made by our very own planet. Scientists call the eerie sequence of quavering whooping sounds "chorus" — and this is one of the clearest examples of the phenomena NASA has ever recorded.
According to The Agency:
Chorus is an electromagnetic phenomenon caused by plasma waves in Earth's radiation belts. For years, ham radio operators on Earth have been listening to them from afar. Now, NASA's twin Radiation Belt Storm Probes are traveling through the region of space where chorus actually comes from—and the recordings are out of this world.
"This is what the radiation belts would sound like to a human being if we had radio antennas for ears," says [Physicist Craig Kletzing], whose team at the University of Iowa built the "EMFISIS" (Electric and Magnetic Field Instrument Suite and Integrated Science) receiver used to pick up the signals.
Intriguingly, the chorus emissions detected by EMFISIS are thought by some to give rise to so-called "killer electrons" — particles with unusually high energy that may pose a threat to satellites and astronauts. Researchers studying the propagation of the radio waves that comprise Earth's chorus, hope to shed light on whether our planet's song is, in fact, responsible for these potentially harmful particles.
Watch the video, and listen to the excerpt of chorus, for more info.