We can’t hear these magnetosonic waves in space. That is because the pressure variations are so small at -100dB sound pressure level (the human hearing threshold is about +60dB). In fact, you’d need an eardrum comparable to the size of the Earth to hear them. Their ultra-low frequencies are also way below what we would be able to hear. So if we can’t hear them, why do we care about them?
Well, in Earth’s “magnetosphere” – the protective magnetic bubble we live in that largely protects us from various dangerous forms of space radiation – these magnetosonic waves can transfer energy around. For example, they can give it to the radiation belts, donuts of radiation surrounding the Earth, creating “killer electrons” at extreme energies that can damage our satellites if we’re not careful. This is why I study these waves – if we can predict when, where and why these waves occur in the space around the Earth, then we could forecast when our satellites might be in trouble and put them into a safe mode.
Recording the inaudible
One of the ways we listen out for these sounds is using geostationary satellites which primarily monitor the weather. As well as all those instruments that can tell you whether to pack an umbrella, they have “magnetic microphones” which can detect these waves. The problem for scientists is separating out all the different types of sound that are present in space. Fortunately, it turns out the human auditory system is pretty good at this sort of thing, some have even called it the best pattern recognition software that we know of. For this very reason, I’m asking for you to lend me your ears.
By amplifying these space sounds and squashing them in time so a whole year becomes just six minutes, they can be made audible. The audio has been uploaded to Soundcloud where you can provide comments on what you think various bits of it sound like. There is so much going on in these sounds, but crowdsourcing comments on them will help identify different types of wave events and ultimately help with the scientific research. So have a listen to some pretty odd sounds from space, because only you can tell me what you hear.