THE eerie sounds of the Northern Lights can be heard even when they’re invisible to the human eye, new research suggests.
Popping, crackling, and even the sound of a rushing waterfall all describe the noises that come from auroras high in the sky.
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And now new research has found that these Northern lights sounds may take place even when we can’t see them.
Acoustic engineer Unto Laine from Aalto University in Finland proved this after recording the ghostly sounds – and on a night when no lights danced in the sky.
Laine unveiled his finding at the EUROREGIO/BNAM2022 Joint Acoustics Conference in Denmark earlier this month.
“This cancels the argument that auroral sounds are extremely rare and that the aurora borealis should be exceptionally bright and lively,” Laine says.
Laine and his fellow colleagues first recorded the strange sounds in 2012.
They also found that the noises were coming from an altitude of about 230 to 330 feet – which is considered low.
However, it wasn’t until 2016 that the researchers uncovered what caused the sounds.
Experts from Science Alert explained: “On particularly cold, clear, calm nights, a layer of warmer air forms above a shallow layer of cold air at the bottom of the atmosphere.”
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“Opposite electrical charges can build up in these two layers; when geomagnetic disturbances, perhaps triggered by the aurora, propagate down through the atmosphere, it can cause an electrical discharge between the layers, which causes the noise.”
The team’s latest findings, which were recorded near the Finnish village of Fiskars, hope to explore auroras further.
“Using the geomagnetic data, which was measured independently, it’s possible to predict when auroral sounds will happen in my recordings with 90 percent accuracy,” Laine said.
This may mean that there is a link between auroral sounds and geomagnetic activity.
And different degrees of geomagnetic activity may be associated with different noises.
However, it’s important to note that the geomagnetic activity that contributes to auroral sounds is different from the activity that produces auroral displays.
In the past, auroral lights have been observed without sounds, and now, the opposite is true as well.
“That was the largest surprise!” Laine said.
“The sounds are much more common than anyone thought, but when people hear them without visible aurora, they think it’s just ice cracking or maybe a dog or some other animal.”
What causes the Northern Lights?
The Northern Lights, also known as aurora borealis, are the result of electrically charged particles from the sun, smashing into gaseous particles in our planet’s atmosphere.
This solar flare is often joined by a coronal mass ejection – which is a huge expulsion of plasma from the sun’s outer layer.
The massive burst of material from the sun prompts a geomagnetic storm, which brings the aurora to lower latitudes.
The solar storms cause bright, colorful dancing lights in white, green, pink, and purple that illuminate the sky and are considered an incredible sight.
Color variations occur when different types of gas particles collide with the charged particles.
The most common color of the aurora is green, which is created when oxygen molecules about 60 miles above the ground react with the particles, whereas nitrogen causes a blue or purple hue.
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This post first appeared on Thesun.co.uk
