Van Allen Probes EMFISIS Waves
Springtime Chorus 2014-03-02

These signals were recorded by the Van Allen Probes A spacecraft EMFISIS Waves instrument on 2014-03-02 during hour 06 UTC. The measurements of three orthogonal magnetic antennas Bu, Bv, and Bw were combined to make this 48-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.

Spring has arrived in the Northern Hemisphere and songbirds are returning. This recording may sound like the song of some strange species of bird, but it is actually a rare falling-frequency variation on chorus emissions which are associated with non-linear processes that may be responsible for transferring energy to trapped electrons in the Van Allen radiation belts and accelerating them to dangerous velocities.