Van Allen Probes EMFISIS Waves
Twisted Chorus 2014-04-05

"Twisted Chorus" -- a new heavy metal band? No, but yet another interesting variation on the chorus waves that may power the acceleration of electrons in Earth's radiation belts. The peculiar S-shaped features in the spectrogram give the appearance of a twisted rope. The pattern of rising and falling tones will challenge any of the theories that exist to explain the discrete features of chorus.

These signals were recorded by the Van Allen Probes B spacecraft EMFISIS Waves instrument on 2014-04-05 during hour 16 UTC. The measurements of three orthogonal magnetic antennas Bu, Bv, and Bw were combined to make the 12-second stereo audio recording.

The video presents a frequency-time spectrogram for the three antennas, with a moving cursor that shows the time position of the audio track. Time advances from left to right along the horizontal axis, frequency ranges from low to high frequencies along the vertical axes, and the amplitude of the signals is color coded with blue indicating weak signals and red indicating strong signals.