NASA’s twin Radiation Belt Storm Probes, launched in late August, recently transmitted recordings of an electromagnetic phenomenon known as “chorus,” caused by plasma waves in Earth’s radiation belts. Chorus is made of radio waves that oscillate at acoustic frequencies between 0 and 10 kHz and is detectible by the magnetic search coil antennas of the probes.
Crais Kletzing of the University of Iowa, a member of the team that built the Electric and Magnetic Field Instrument Suit and Integrated Science (EMFISIS) receiver used to pick up the signals, describes the chorus as “what the radiation belts would sound like to a human being if we had radio antennas for ears.” Though the data is currently sampled at 16 bits, the probes do have the capability to record in stereo; Kletzing hopes to eventually use the stereo capability to determine how broad the region is over which chorus occurs.
