Aurora borealis

Courtesy of WARREN GAMMEL

Aurora borealis lights up the sky.

Can you hear the aurora borealis?

In a word, yes. Humans and animals, particularly dogs, react to sounds that we have never been able to record. But it may not be exactly what people think they hear.

Reports of hearing the aurora are rare. Most people report hearing sounds they associate with the aurora once or twice in a lifetime. Northern indigenous residents may say that they hear them often, but their reports are rarely documented.

Some say they hear a swishing sound like that of a taffeta skirt, or burning grass, frying grease, crumpled paper rubbed in the hands or like static electricity. Generally, they don’t hear it very long — from a few seconds to a few minutes. 

The science around the sound of the aurora is scarce. However, we do have a few highly reliable reports from scientific observers. During the great aurora of Jan. 25, 1938, leading aurora scientist Carl Stormer and his assistant heard auroral sounds for more than 10 minutes. They heard it only when the aurora was overhead.

Most of the time, but not always, people report seeing the aurora before hearing the sounds. They also typically report that they hear the sound in sync with the movements of the aurora. They tend to associate it with fast-moving displays, especially when it is overhead.

Because of this, scientists ask whether they are hearing the aurora itself — and the laws of science are behind their skepticism.

A person cannot simultaneously see and hear the aurora because of the difference between the speed of light and the speed of sound — sound travels much slower than light. With the aurora 60 miles above the observer, it would take several minutes for the sound to travel that distance.

The real question isn’t whether the aurora makes noise, it’s whether it’s making the noise people say they hear. 

Auroral processes acting in the high ionosphere do generate sound waves of very low frequency with periods of about 10 seconds. These sounds have been recorded on instruments as they reach the ground, but it’s not instantaneous — it takes about five minutes.

Meteoroids break up in the atmosphere all the time and we hear their sound minutes later. On super-rare occasions, they have been nearly  simultaneous when the meteoroid breaks up in a violent explosion within 18 miles of the surface of the Earth.

Rarely, observers report smelling ozone while hearing aurora.

What’s also interesting is that no one has reported hearing aurora australis. All reports so far are from the Northern Hemisphere aurora oval zone. Another problem is that most reports do not give complete information, such as the exact date, time and conditions.

The question of people reporting they’re hearing something at the same time they watch the northern lights does lead to other questions.

Is there a physiological human or body response in sight or sound? Is what the eye sees fooling the ear into thinking there should be a sound? Is it cross-talking in the brain?

A compounding problem is that people’s memories aren’t always exact. Think about people who witness a car accident and a few hours or weeks later they are in a courtroom and come up with different interpretations of what happened.

The science is spotty.

There have been a few situations where scientists have been blindfolded with soundproof earmuffs on and told to tell others if they hear the auroral sound. The other scientists do not speak or make any movements so as not to give any clues to the hooded person wearing soundproof earmuffs. It is unknown what the results of these are.

What we are left with is the idea that the human body’s eye, ear and nose detectors are superior to most instruments. However, a human’s data processing center is subjective and prone to error, and our memories are very selective and often deteriorate over time.

What it comes down to is that auroral sound is a real physiological phenomenon and it is created very close to the observer: in the air around him, in ice crystals on the ground or nearby trees.

Presumably, all this has been created by some sort of electric field effect. We have a good understanding of the 300,000-volt global electric field that lies above 125 miles from the Earth that is kept from discharging the insulating effects of the air in the Earth’s atmosphere.

We have no documented instrumented instances of it reaching where a person might be standing on the Earth, but maybe we just have not been at the right place at the right time with our instruments.

Dr. Neal Brown, geophysics professor emeritus at the University of Alaska Fairbanks (UAF), is a world authority on the aurora borealis. 

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