The above recording was made on June 27, 1996.
It was made by the Galileo spacecraft as it passed Ganymede
a moon of Jupiter.
At about 8 seconds in, Galileo enters Ganymede’s magnetosphere
there is a sudden increase in noise, sounding like a clap of thunder.
As the spacecraft passed through the magnetosphere, the
noise rose in pitch to peak, then decreased again.
The irregularities in the recording, such as the sudden drop
in volume at 15 seconds, are caused by irregularities in the
magnetosphere of Ganymede as it passes through the
influence of the immense magnetic field of Jupiter.
Sounds Of Ganymede's Magnetosphere
An antenna on the spacecraft was picking up plasma waves
created by the unusually strong magnetosphere of Ganymede
about 3 times stronger Mercury.
This was used to create an audio signal (below, the 45 minute
signal is compressed into about 60 seconds), where the sound
frequency corresponds to the frequency of the waves detected.
Regards