Even if we’re not seeing the Northern Lights, their ghostly sounds may just as well be dancing in the air: a new study suggests they take place high in the atmosphere even when we can’t hear them. According to scientists, perhaps they are also present when we cannot see the boreal show.
A new study conducted at Aalto University in Finland has found that acoustic phenomena Aurora-related events are much more common than previously believed and occur even in the absence of visible auroras in the sky.
According to the acoustic engineer Unto Laineauthor of the study published in ResearchGate, the finding allows us to verify that the sounds of the auroras are not extremely rare and that the Aurora borealis they do not have to be exceptionally bright and lively for the sound emissions to materialize.
Deciphering the sound of the auroras
According to a press release, Laine and his team have been working on this phenomenon for more than a decade. In 2012, they found that the sound emitted by an aurora borealis It is similar to the snap of static electricity or the one that occurs when we walk on a field full of dry leaves.
Nevertheless, many of these sounds are not audible to humans, because they occur far from the earth’s surface, in the highest layers of the atmosphere. In 2016, Laine managed to link recordings of crackles and pops during an auroral event with temperature profiles measured by the Finnish Meteorological Institute (FMI).
The data again showed that auroras are related to sounds, but also supported the theory held by the Finnish specialist that these acoustic emissions are the result of electric shocks that occur in the sky, generated by variations in the magnetic field from the earth.
Now, in new research presented at the Joint EUROREGIO/BNAM Acoustics Conference 2022 in Denmark, Laine managed to capture hundreds of auroral sounds using nighttime recordings made near the town of Fiskars in southern Finland. When the records were compared with the geomagnetic activity measurements carried out by the Finnish Meteorological Institute, a strong relationship between the two phenomena became evident.
Thus, it was found that 60 sounds recorded by Laine were all related to changes in the earth’s geomagnetic field. The scientist concluded that using the geomagnetic data, which was measured independently, it is possible to predict when the sounds of the auroras will occur in the recordings with a 90% accuracy.
In summary, statistical analysis suggests a causal link between geomagnetic fluctuations and aurora sounds. The most surprising finding, however, is that auroral sounds occur even in the absence of visible Northern Lights.
This means that the sounds are much more common than previously thought, especially in good weather conditions: however, given the impossibility of appreciating the phenomenon in the sky, can be easily confused with other natural soundssuch as those emitted by animals.
Sound producing mechanism in the temperature inversion layer and its sensitivity to geomagnetic activity. Unto Kalervo Laine. Researchgate (2022).