Van Allen Probes EMFISIS Waves
Whistler Wars 2015-04-30

Just in time for May the 4th, this sounds like the whole rebel alliance fleet attacking the death star, but, amazingly, this is real. These signals were recorded by the Van Allen Probes A spacecraft EMFISIS Waves instrument on April 30, 2015, between about 08:34 and 08:42 UTC. The measurements of three orthogonal magnetic antennas Bu, Bv, and Bw were combined to make the 54 second stereo audio recording.

These signals, called whistlers, are created by lightning discharges in Earth's atmosphere which then propagate back and forth along magnetic field lines with lower frequencies being delayed as they travel through the thin charged gas of space. The resulting spread in frequency produces a whistling tone with the dispersion related to the quantity of plasma the signal has traversed. The result sounds just like movie sound effects!

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.