Van Allen Probes EMFISIS Waves
Whistler Triggered Emission 2013-06-13

The Van Allen Probes EMFISIS Waves instruments detected these signals with three orthogonal magnetic antennas (Bu, Bv, Bw) during UTC hour 08 of June 13, 2013. The most prominent signals in this clip are lightning whistlers that decrease in frequency with time. Some of them are quite intense and it is believed that these whistlers can trigger some of the other rising tones in this example. The rising tones are easily seen in the spectrogram, but you have to listen carefully for them at very high audio frequencies in this clip. That one emission (a whistler) can trigger other emissions (the rising tones) is an example of the complex and non-linear phenomena found in Earth's radiation belts.

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