Oct. 1, 2012: In space, they say, no one can hear you scream.
Nobody ever said anything about singing, though. A NASA spacecraft has just beamed back a beautiful song sung by our own planet. "It's called chorus," explains Craig Kletzing of the University of Iowa. "This is one of the clearest examples we've ever heard."
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.
"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.