Van Allen Probes EMFISIS Waves
Chorus from 2012-12-10

The Van Allen Probes EMFISIS Waves instruments detected these signals with three orthogonal magnetic antennas (Bu, Bv, Bw) during UTC hour 04 of December 10, 2012. The predominant feature is yet another variation on low-frequency chorus. This is a bit quieter and more subtle than what has been presented previously. One might call it sotto voce. Note the presence of rare falling tones in the lower frequency component.

Chorus waves in Earth's magnetosphere are generated in the Van Allen radiation belts by electrons spiraling along Earth's magnetic field lines in this region. Once generated, the chorus waves interact with the moving electrons, either accelerating them to higher energies or disturbing the spiral orbit of the electrons and causing them to fall into Earth's upper atmosphere along the magnetic field lines.

The animation shows a frequency-time spectrogram of the data with a moving cursor that indicates the time position of the audio track.