Auroras are some of Earth’s most spectacular natural phenomena. Travelers come from far and wide to see the incredible Northern Lights and wonder at their beauty. Once thought to be magical in nature, most science fans understand that the lights are formed by the solar wind interacting with our magnetosphere. But did you know they also make sounds?
This isn’t new news – researchers have thought there was a connection for over a decade. In fact, a now Emeritus Professor at the University of Aalto, Unto K. Laine, first recorded what he thought to be auroral sounds back in 2004. They sounded like a series of pops and cracks, but Dr. Laine eventually linked up a series of them to a set of temperature changes recorded by the Finnish Meteorological Institute.
With that data, which was published in a paper in 2016, Dr. Laine was finally able to draw a possible connection that he had been studying. He believed that the sounds were actually caused by electrical discharges across a “temperature inversion layer” of air about 70 meters off the ground. The data lent credence to this idea.
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Those electrical discharges aren’t necessarily visible; however, the pops still happen despite the lack of a visible cause. What’s more – they happen a lot more often than there are visible causes. To Dr. Laine, at least, this means that auroras are much more common than typically thought, even if they aren’t necessarily visible.
Tracking auroras themselves requires geomagnetic readings, and plenty of those matched up with the timing of the auroral sounds Dr. Laine collected in his latest recording near the village of Fiskars, the original home of the multinational company of the same name. Using geomagnetic data alone, Dr. Laine could estimate when the sounds would happen with 90% accuracy. The 60 best sounds he recorded were all directly tied to geomagnetic events.
So what does all this data collection actually mean? The simplest explanation is that the popping and cracking sounds recorded by Dr. Laine and numerous others are clearly tied to the same geomagnetic processes that create the visible auroras. However, the precise location and cause of the sounds are still being debated, though a dramatic temperature variant about 70 m off the ground could conceivably create an electrostatic discharge that could be picked up as a click.
But the most surprising finding, at least according to Dr. Laine, is just how often these sounds occur. The sounds that he describes as akin to “ice cracking or someone walking a dog” are caused by the same geomagnetic forces that create the famous lights and are much more common than the lights themselves. So if you’re ever inspired to see this world-famous natural phenomenon, it might be a good idea to bring along a recording device. Then, if you don’t get a chance to see the lights themselves, you’ll at least be able to hear them.
Aalto University – The aurora borealis can be heard even when they can’t be seen
UT – Mysterious Sounds Made by the Aurora Borealis
UT – The Northern and Southern Lights – What is an Aurora?
UT – An 1874 Citizen Science Project Studying the Aurora Borealis Helped Inspire Time Zones
Image of some spectacular auroras in Finland.
Credit – Seppo Fagerlund