Professor Emeritus To K. Laine of Aalto University made recordings of the aurora that show the phenomenon is much more common than previously believed and occurs even in the absence of visible northern lights. “This cancels the argument that the aurora sound is extremely rare and that the aurora must be particularly bright and vivid,” says Laine.
Laine has been studying the sounds associated with the Northern Lights for many years. In 2016, he published a linked article recording of crackling and popping sounds during an aurora event with temperature profiles measured by the Finnish Meteorological Institute (FMI). These data not only demonstrate that auroras are sometimes associated with sound, but also support Laine’s theory that sound caused by discharge through the temperature inversion layer about 70 meters above the ground.
The new recordings were made at night near the village of Fiskars. Although no northern lights were seen, Laine’s recordings recorded hundreds of ‘aurora sound’ candidates. When the records were compared with the FMI’s measurements of geomagnetic activity, a clear correlation was evident. The 60 best candidate sounds are all related to changes in the geomagnetic field.
“Using independently measured geomagnetic data, I was able to predict when the aurora borealis occurred in my recordings with 90% accuracy,” says Laine. His statistical analysis revealed a causal link between geomagnetic oscillations and the aurora sound.
For Laine, the most striking finding was the fact that the aurora borealis occurs even when there is no visible northern light. ‘That was the biggest surprise! These sounds are much more common than people think, but when people hear them without seeing the aurora, they think it’s just the breaking of the ice or maybe a dog or a dog. some other animals’, he said.
The source: University of Aalto
