It’s a question that has puzzled observers for centuries: Do the brilliant green and red light displays of the aurora borealis produce any discernible sound?
Due to the interaction of solar particles with gas molecules in Earth’s atmosphere, auroras typically occur near Earth’s poles, where the magnetic field is strongest. However, reports of aurora making noise are rare – and have historically been dismissed by scientists.
But a Finnish study in 2016 claimed to have finally confirmed that the northern lights do indeed produce sounds audible to the human ear. A recording made by one of the researchers involved in the study even claimed to have captured the sound made by panoramic lights 70 meters above ground level.
Still, the mechanism behind sound remains somewhat mysterious, as do the conditions that must be met in order to hear sound. My recent research takes a look at historical reports of the Auroral Sound to understand the methods of investigating this elusive phenomenon and the process of establishing whether the reported sounds were objective, fictitious.
Auroral noise was the subject of particularly lively debate in the first decades of the 20th century, when accounts of settlements in northern latitudes reported that the sound was sometimes accompanied by fascinating light displays in their skies.
Eyewitnesses reported a quiet, almost imperceptible hoarse, particularly hoarse or whistling sound during violent northern lights displays. For example, in the early 1930s, a flood of personal evidence appeared in The Shetland News, a weekly newspaper for the suburban Shetland Islands, comparing the sound of the northern lights to “rustling silk” or “flats consisting of two planks”. manner”.
These stories were corroborated by similar testimony from northern Canada and Norway. Yet the scientific community was less than convinced, especially as very few Western explorers claimed to have heard the elusive noise.
From this time the reliability of auroral noise reports was closely tied to height measurements of the northern lights. It was believed that only those displays that descend down into Earth’s atmosphere would be able to transmit sound that could be heard by the human ear.
The problem here was that results recorded during the Second International Polar Year of 1932–3 found that auroras occur most often at 100 km above Earth and rarely below 80 km. This suggested that it would be impossible to transmit sound clear from light to the Earth’s surface.
Given these findings, eminent physicists and meteorologists remained skeptical, dismissing the auroral sound and the much smaller aurora as folklore or auditory illusions.
Sir Oliver Lodge, a British physicist involved in the development of radio technology, commented that auroral sound may be a psychological phenomenon due to the apparent appearance of aurorae – as meteors sometimes project a whooshing sound into the brain. Similarly, meteorologist George Clarke Simpson argued that the appearance of fewer aurorae was an optical illusion caused by interference from low clouds.
Nevertheless, the leading auroral scientist of the 20th century, Karl Stormer, published articles written by two of his assistants who claimed to have heard aurorae, adding some validity to the large amount of individual reports.
Stormer’s assistant Hans Gelstrup said that he heard “a very curious faint whistling sound, clearly wavy, which exactly follows the vibrations of the aurora”, while Mr Tjön described “burning grass or spray”. Like felt the sound. As these two final evidences may be, he still has not proposed a mechanism by which auroral sound may operate.
sound and light
The answer to this enduring mystery that has since gained the most support was first suggested by Clarence Chant, a renowned Canadian astronomer, in 1923. He argued that the movement of the northern lights alters Earth’s magnetic field, causing changes in the electrification of the atmosphere even over significant distances.
This electrification produces a crackling sound very close to the Earth’s surface when it meets objects on the ground, much like the sound of a still. This may be on the observer’s clothing or glasses, or possibly in surrounding objects including pine trees or the covering of buildings.
Chant’s theory correlates well with several accounts of auroral sound, and is also supported by occasional reports of the smell of ozone – which reportedly carries a metallic odor similar to that of an electrical spark – in displays of the northern lights. during.
Yet Chant’s paper went largely unnoticed in the 1920s, only gaining recognition in the 1970s when two auroral physicists revisited the historical evidence. The principle of chanting is largely accepted by scientists today, although there is still debate as to how the mechanism for producing sound actually operates.
What is clear is that the aurorae, on rare occasions, make the sound audible to the human ear. Terrifying reports of hoarseness, whistling and buzzing accompanied by lights describe an objective audible experience – nothing illusory or imagined.
If you want to hear the northern lights for yourself, you may have to spend a lot of time in the polar regions, given that the aural phenomenon is only represented in 5% of violent auroral displays. It is also commonly heard on top of mountains, which are surrounded by only a few buildings – so it is not a particularly accessible experience.
In recent years, the sound of the aurora has been explored for its aesthetic value, persuasive musical compositions, and laying the foundation for new ways of interacting with its electromagnetic signals.
Latvian composer Erik Eisenwalds has used journal extracts from American explorer Charles Hall and Norwegian politician Fridjtof Nansen, both of whom claim to have heard the northern lights in their music. His composition, Northern Lights, combines these reports with the only known Latvian folklore recounting the auroral sound phenomenon sung by a tenor solo.
Or you can also listen to the radio signal of the northern lights at home. In 2020, the BBC 3 radio program remapped very low-frequency radio recordings of aurora to the audible spectrum. While this is not the same as perceiving the audible noise produced by the northern lights on a snowy mountain top, these radio frequencies give a terrifying sense of the fleeting, fleeting and dynamic nature of aurorae.