Van Allen A 2013-03-21 periodic chorus

The Van Allen Probes EMFISIS Waves instruments detected these signals with three orthogonal magnetic antennas (Bu, Bv, Bw) during UTC hour 00 of March 21, 2013. We see even more variety in these chorus emissions with their intensity rising and falling every few seconds in a periodic way. This is a phenomenon which has been noticed in the past but our understanding of why this happens is not yet complete.

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.…