Have You Heard an Aurora?
Auroras, commonly known as the "northern or southern lights", are spectacular light shows resulting from the interaction of charged particles from the Sun with the atmosphere of the Earth. Such events are quite frequently seen from high northern or southern latitudes: only during times of large geomagnetic disturbance (such as March 13-14, 1989) are they seen from more equatorial latitudes.
Whilst they are a spectacular sight, less well known are intriguing reports of sounds being heard during auroral displays. As yet these sounds have not been recorded on any instrument, and to deepen the mystery, at times only some members of a group report hearing them. With such scant evidence, we must be wary about the reality of the phenomena.
Niel Davis in the book The Aurora Watchers Handbook indicates that there are around 300 documented reports of auroral sound and a number of these come from technically trained people such as scientists. There is good consistency in the description of the sound being heard - at least 80 percent mention the letter "S" in the description and most report that the sound is a variable or undulating hissing, swishing, whooshing or crackling noise. Descriptions include: "the swishing of a taffeta skirt"; "burning grass"; "the sound of crumpled tissue lightly rubbed between the hands"; and "the sound of a comb being drawn through a woman's hair".
The sounds last from a few seconds up to some tens of minutes and many reports indicate a combination of a hissing sound followed by a sharper crackling. In general the sounds were not loud, but were quite definitely able to be heard. In most cases all members of a group would hear the sounds but there are reports of not all members hearing them. There have also been cases where people separated by hundreds of metres have all heard the sounds.
An example of a report of auroral noise comes from Dr. H. D. Curtis, astronomer in charge of the Labrador Station of the US Lick Observatory in 1906. The report was later published in the September 1921 edition of the reputable "Science" journal:
The station was located at Cartwright...and auroral displays were frequent and bright during July and August. On several nights I heard faint swishing, crackling sounds, which I could only attribute to the Aurora. There were times when large, faintly luminous patches or "Curtains" passed rapidly over our camp; these seemed to be close, and not more than a few hundred feet above the ground, though doubtless much higher. The faint hissing and crackling sounds were more in evidence as such luminous patches swept past us...I tried in vain to assign the sounds heard to some reasonable source other than the aurora, but was forced to exclude them as possible sources; besides, what I heard didn't sound like anything from anything I could postulate.....In short, I feel certain that the sounds I heard were caused by the aurora and nothing else. There was, moreover, a certain synchronism between the maxima of these sounds and the sweeping of auroral curtains across the sky.
Fact or fiction - the evidence of witnesses seems good but could they all be responding to the same psychological phenomena. Without hard evidence such as a recording there is no way to be sure at present. And if the reports are real, there is the tricky problem of the mechanism by which the aurora, 60-80 km above the Earth's surface, generates the sound which people hear?
Based on information in The Aurora Watchers Handbook by Niel Davis (University of Alaska Press, 1992).