Earth’s Massive Magnetic Musical Instrument | Magnetospheric Resonances | SSFX Space Sound Effects


Let me play you a tune. What do you think? OK, yes that wasn’t actually a piano you were hearing and in fact I wasn’t even playing it. What that was was Earth’s massive magnetic musical instruments. Of course what I’m talking about here is Earth magnetosphere. This is the region of space around the Earth which is dominated by Earth’s magnetic field and it’s shaped by its interaction with the solar wind, carving out a magnetic bubble that we live in that protects us for many of the sources of space radiation. In my video about the tagline to Alien being wrong, I told you what sound in space physically is, but the shape of Earth’s magnetosphere and the speeds the waves can travel at at every point within massively affect these sounds. It’s very much akin to say a musical instrument and I’m going to tell you why. The notes of musical instruments and the way they sound come from standing waves or resonances. Asimple way to understand these is with a stringed instrument. Pluck a string and a vibrational wave will travel along it until it reaches that fixed end of the string. At that point it can’t go any further, it gets reflected back interfering with the original wave. If you tune that original wave to be just right in a way that whole number of waves fit onto the string, it forms a standing wave. These are wave patterns which don’t appear to move, they just go up and down in amplitude. So the natural frequencies of things like a string come from a combination of how long that string is and how fast those waves travel along it. These same musical principles occur for the sounds in space. Remember that a magnetic field line can be thought of as something like a string under the tension and these field lines are fixed where they meet Earth’s ionosphere at the northern and southern ends, just like you have in a piano or say a guitar. So we can have a standing waves of these field lines, known as field line resonance. But these are the only instruments that Earth’s magnetosphere is like. Magnetosonic waves can bounce around between boundaries within the magnetosphere. So regions of the magnetosphere act something like a cavity, a waveguide or, in say more musical terms, a resonanting chamber. And finally the outer surface of the magnetosphere where it meets the solar wind is a membrane, very much like a drum. Back in the nineties when I was probably listening to the Spice Girls and watching Friends, the idea was put forward that Earth’s magnetosphere had a set of notes, the frequencies it like to oscillate at. This was supported by the small amount of data we have available at the time, but was a bit of a question. You see the size of the magnetosphere varies depending on the solar wind and this is not constant, it’s always changing. And the speed of waves within the magnetsosphere also change. This is why the particular notes of the magnetosphere that had been proposed were given the nickname of “magic frequencies”. No they weren’t proposing that space wizard was playing Earth’s magnetic field, it was that these frequencies were “magically” somehow incredibly stable – the magnetosphere was an instrument that didn’t need retuning every now and then. It became a rather controversial topic as more and more data came in – some purported to detect special magic frequencies, others said there was no significance in them whatsoever. And what I’ve been working on is trying to work out exactly how all of the different sounds in space should change in frequency depending on the changing conditions. Essentially how “magic” are “magic frequencies”. All my work so far doers seem to suggest that they should be incredibly variable, but there’s still more work to do to really prove this. So I hope you appreciate that while Earth’s magnetosphere is something of a massive magnetic musical instrument, it is probably one of the most complicated musical instruments that exists and the task of researching into sounds from space is trying to pull apart a symphony of different notes that have been played in different ways and trying to uncover the mystery of not only the player, but the composer as well. Thank you so much for watching this video as part of my SSFX series. Please check out the other videos and check out the film competition that goes along with it. And I would appreciate any likes, shares or subscribes you may feel to give me. I’ll see you soon.