The mysterious sounds that can be heard during the polar auroras would be due to electrical discharges that occur at about 75 meters above sea level, in the so-called temperature inversion layer.
To propose this new hypothesis to explain the enigmatic sounds, often described as the distant noise of a large waterfall, are the researchers of the Finnish University of Aalto led by Unto Kalervo Laine, on the occasion of the Baltic Nordic Acoustic conference organized in Denmark, to Aalborg.
For centuries there have been testimonies of strange sounds associated with the appearance of the polar auroras, sometimes described as crackling, distant applause or the sound of waterfalls.
Few, however, had so far been able to give a convincing explanation of the phenomenon.
Despite the many testimonies, even starting with the prophet Ezekiel 600 years before Christ, some experts continued to consider the phenomenon a sort of illusion because the auroras are phenomena that occur very high up, in areas of the atmosphere that make it impossible to propagation of a sound down to the ground.
After more than 20 years of analysis, the Finnish research team may now have found a compelling explanation.
According to scholars, sounds and auroras are actually two distinct phenomena: as they are both linked to the interaction of solar particles with the Earth's magnetic field, they often occur simultaneously, but are due to different physical mechanisms.
The sounds depend on electrical discharges in the so-called temperature inversion layer, a kind of heat transition belt that is generated only in certain weather conditions, particularly in the absence of wind and clouds, and which is normally found between 75 and 100 meters in height.
Auroral sounds may be more common than expected and may even be used to anticipate actual auroras.