A NASA spacecraft has recently for the first time ever recorded the sound of the earth’s electromagnetic plasma waves. The sound is referred to as a ‘chorus’ and it is made up of radio waves, it sounds like this.
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 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.
He’s careful to point out that these are not acoustic waves of the kind that travel through the air of our planet. Chorus is made of radio waves that oscillate at acoustic frequencies, between 0 and 10 kHz. The magnetic search coil antennas of the Radiation Belt Storm Probes are designed to detect these kinds of waves. “Chorus emissions are front and center for the Storm Probe mission,” says Kletzing. “They are thought to be one of the most important waves for energizing the electrons that make up the outer radiation belt.”
In particular, chorus might be responsible for so-called “killer electrons,” high-energy particles that can endanger both satellites and astronauts. Many electrons in the radiation belts are harmless, with too little energy to do damage to human or electronic systems. But, sometimes, these electrons can catch a chorus wave, like a surfer riding a wave on Earth, and gain enough energy to become dangerous—or so researchers think.
Learn more about future missions to record more of these sounds from our planet at NASA.