One of the ongoing debates among skywatchers of all kinds has been: Do aurorae make noise? For thousands of years, people have reported noises associated with these magnificent sky displays, but like researchers trying to document ghosts, consistent and rock-solid evidence has eluded capture.

But maybe that is changing.

In the cold north of Finland, Professor Emeritus Unto Laine has been using his retirement years to seek out auroral sounds and define the conditions that make them possible.

Aurorae occur when solar particles interact with our atmosphere and transfer their energy to gasses in the sky, which get excited and glow. Oxygen can shine red or green, and nitrogen adds highlights of blues and purples. That glowing gas is often tens of miles to over 150 miles up. That isn’t what we’re hearing.

Laine has been looking for an effect more down toward Earth and theorized that electrical discharges can occur where a layer of warm air builds between two cooler layers. Called a temperature inversion layer, these kinds of warm air regions can be found 70 meters up, which is a distance that you are close enough to hear.

Laine recorded audio while measuring geomagnetic data. He found sixty candidate sounds all linked to changes in the geomagnetic field. According to Laine: Using the geomagnetic data, which was measured independently, it’s possible to predict when auroral sounds will happen in my recordings with 90% accuracy.

This work, which is presented at the Joint Acoustics Conference in Aalborg, Denmark, suggests that the same kinds of conditions that can be linked to aurorae can be linked to these sounds. This means you can have sounds without aurorae and aurorae without sound, but both activities require our Earth’s magnetic field to be fluctuating due to something like solar activity.

So do aurorae make sounds? No. Do the conditions that make aurorae possible also sometimes lead to crackling electrical discharges we can hear. Yes.

Are their ghosts? We still have no evidence for that.

More Information

Aalto University press release

“Sound producing mechanism in temperature inversion layer and its sensitivity to geomagnetic activity,” Unto K. Laine, 2022 May, BNAM2022 Baltic-Nordic Acoustic Meeting