Until the static snaps through, all you hear is the difference between the ambience of the recording and that of the room you’re in, the uneasy noise that strains your ears around the assurance there’s something there to be heard. The static itself is dynamic enough to pass as the stock sound effect of a crackling fire. Then in swells you make out the signals: first a single burst, like a seagull call passed through a ring modulator, its echo, the echo of the two combined, and so on. As they gather, and bleed together, you make out a third noise: long and soft swooping signals that sound like they should accompany a ‘shutting down’ command. They rise and fall with a kind of sonic Doppler effect. If wind were electric, this is what it would sound like.
They’re the sound of the earth, or rather, the amplified sound of the very low frequency (VLF) radio interaction of solar energy with the earth’s magnetosphere. Those electronic birds are known as auroral chorus, and the soft swoops are called whistlers. Together they comprise a spectrum of natural radio, or auroral, waves. And though they sound ‘electronic,’ they far precede any circuit or signal produced by man. In fact they precede most things, by virtue of their cosmic origins. They might not be able to hear you scream in space, but with a few bits of basic equipment you can hear the little-known natural sound of the world around you.
Their visual equivalent tends to hog all the attention, not to mention the tourists. A clue: they’re big, green, and seem to thrive in remote mountainous regions. No, not Ray Mears. Sure, the Aurora Borealis are a once-in-a-lifetime experience, and stir a certain awe towards the world’s infinite wonders, etc, etc, which lends them to any momentous occasion you care to throw in their vicinity. And yes, by comparison, in our hypervisualised and hypersensitive world it would no doubt be considered unromantic to propose with headphones on, not to mention a home-made coathanger aerial standing between you and your loved one. A bad signal if there ever was one. But auroral waves really do deserve
just a little more renown.
While the socked and sandaled patrons of the Northern Lights gawp wide-eyed, I recommend you listen. But if you really need a visualisation, take a look at the spectrograms produced by the waves. The VIP of VLF, Stephen McGreevy, recorded this image of the whistlers he heard in northern Navada, and this one of a strong daytime chorus signal in central Alaska. Remove the grid and the images could be brushstrokes: a vague background texture of white noise shot through with deliberate, discernable marks. From the sounds and accompanying spectrograms, scientists are able to ‘read’ space weather. The charged particles (ions) that make up the solar winds stream towards planets and collide with their magnetosphere, creating electromagnetic signals which can be amplified from their native range of between 100 and 10,000 cycles-per-second (0.1 – 10 kHz) to frequencies audible to humans. Sudden bursts of energy produce correspondingly sudden, stronger signals, and so on.
NASA has even released several recordings made by Voyager, of the auroral sounds of the planets of our solar system. For the intergalactic price of $118 you can get a (used) copy of the seminal ‘Symphonies of the Planets’ from 1992. Jupiter is metallic, like a gong that simply sustains, or the chanting mouths of monks; Uranus sounds windy, as though jet planes were zooming overhead in every direction; while our beloved Earth sounds like it’s being buffeted by a blizzard, or like there are aircraft performing scrappy manoeuvres, forever about to take off.
Compared with these meditative drones, the Jupiter movement of Gustav Holst’s famous ‘Planets’ suite sounds ridiculous. You can imagine the latter playing as, in the opening scene, an elegant spaceship goes into superduperhyperdrive. Mute a little of the dissonance, and it could just as easily back a Western. It’s the flat-packed music of Pioneers – in the sense of the foremost explorer – adaptable to any adventure. The timid sections are curious, rather than humble. A glockenspiel rings above the orchestra, gilding its success, and the main theme (you’ll know it) feels almost regal. You can picture man disembarking, ready to civilise with his Western canon of catchy tunes. Each repetition of that theme gets slower, more demanding of reverence.
Auroral waves are the true sound of the planets, perhaps if nothing else in the sense that they must be taken as an imperfect translation of the reality: transformed from an otherworldly energy to one we can comprehend, but which we must always acknowledge as indirect, having squeezed it through our narrow doors of perception. That knowledge lends a scale to the ambience of these sounds which conveys a sense of deep space far more effectively than any ‘traditional’ musical rendering could. Interestingly, they seem to go some way to confirming the aesthetic curated by the fictional world of sci-fi, created much later than but known to us much earlier than its natural counterpart. The sounds of all the lasers, teleport devices, warp engines, and extraterrestrial landscapes you could ever want have been there for millennia, zipping around us, ignorant until we look and listen up.