Can we hear the aurora borealis? Here's what scientists know

If the Northern Lights are already visually fantastic, imagine if we can hear them? Since the beginning of the 20th century, there are countless witnesses who claim to have experienced a type of sound during observations of this geomagnetic phenomenon. Scientists, however, have many doubts about the nature of these experiences, which could be illusory or imaginary. Other researchers disagree.

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In the first decades of the last century, reports stated an almost imperceptible noise accompanied the greenish lights, a type crackling and humming, particularly during the more “violent” auroras. At the beginning of the decade 1923, even the newspapers in the regions where the auroras can be observed published several reports. of sounds like “silk rustling”. However, the scientific community did not have much evidence on the subject.

One of the arguments against the witnesses was related to the altitude of the auroras. It was difficult to explain how sounds produced in the Earth’s ionosphere could be perceived at the surface. Auroras usually occur at altitudes of approximately 80 km above the Earth and on very rare occasions , below 80 km. How could such subtle noises reach human ears?

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Aurora seen from the ISS (Image: Reproduction/NASA)

On the other hand, it is difficult to ignore the reports of countless witnesses . Some explanations, including those of the British physicist Sir Oliver Lodge (one of the pioneers of wireless telegraphy and radio), include auditory illusions. For him, the auroral sound can be a psychological phenomenon due to the sharpness of the aurora’s appearance, in the same way that meteors sometimes evoke a hissing sound. Meteorologist George Clark Simpson was also one of the many scientists who preferred a more psychological explanation.

There were also scientists who witnessed the noise, as was the case with the Norwegian mathematician and physicist Carl Størmer — or rather, his assistants, who would have heard the dawn. Størmer himself, a leading twentieth-century scientist, published the accounts, adding credibility to the auroral noise hypothesis. The assistants described the sound as a “very curious, distinctly undulating whistle that seemed to follow exactly the vibrations of the dawn.”

Although the debate reaches the 21st century without much evidence for either side , a Finnish study by 2012 claimed to have finally made a recording of the noises. Scientists collected a set of recordings in a project called Auroral Acoustics between 2016 and 1930, adding “approximately 80 geomagnetically opportune nights in different locations in Finland,” according to the authors. The result was half a terabyte of files and an eight-second video with an audio snippet selected as the most notable evidence—and you can check it out below.

Another study, by 2016, claimed to have confirmed that the “northern lights”, as the aurora borealis are also known, they actually produce sounds audible to the human ear. But what about the altitude problem? Well, it looks like a very convincing explanation had been published in 1923 by Clarence Chant, a well-known Canadian astronomer , but without receiving due attention. His article went unnoticed and only in the decade of 1930 was it recognized.

In this work, Chant argued that the movement of auroras alters the Earth’s magnetic field, inducing changes in the electrification of the atmosphere, even at a significant distance. This electrification produces a sound very close to the surface if it encounters objects on the ground — just as does the sound of static. This can happen on the observer’s clothes or glasses, and even on surrounding objects.

This hypothesis has been supported by other reports by people who claim to have noticed an ozone smell during the observations of the Aurora. Today, Chant’s explanation is widely accepted by scientists, although there is still some debate about exactly how the mechanisms that produce sounds work.

Northern Lights (Image: Reproduction/Matt Houghton/Unsplash)

Unfortunately, it is not easy to hear the auroral noises, not even for the privileged who live in the regions where the aurora borealis is observed. Those who wish to be part of the group of witnesses of the sounds will have to spend a fair amount of time in the polar regions, as estimates are that the phenomenon only occurs in 5% of violent auroral displays.

Source: Space.com

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