Can you hear the Northern Lights?
Yesterday I posted a beautiful photo of an aurora. One of my readers, Spokesrider, added this very interesting comment: Oh, my. That is a great photo. I've never seen any quite like that myself, especially not here in southwest Michigan USA. But I am one of those strange people who claims to have heard northern lights. They woke me up once, and eventually I figured out that the noise was not coming from the pump in the basement, but from the northern lights in the sky. I swear it!
Well, I hadn't heard of this before, and it sounded like an interesting question, so I did a little research, and came up with a couple of leads. First, the Wikipedia article on auroras has this paragraph under the heading "auroral sounds":
Throughout history people have written and spoken of sounds associated with auroral displays, often describing them as crackling, hissing, buzzing, or whistling. Danish explorer Knud Rasmussen mentioned them indirectly in 1932 while describing the folk traditions of Greenland Eskimos. The same sounds in the same context are mentioned in an account written by Canadian anthropologist Ernest Hawkes in 1916. Cornelius Tacitus (AD 56-120), an ancient Roman historian, wrote that people from the north of (modern) Germany claimed to hear them..
Today, many people continue to report these sounds, but despite their many anecdotal reports, nobody has yet managed to record the sounds, and there are scientific problems with the idea of the sounds being true sound waves originating in the auroras. The energy of the auroras and other factors make it extremely improbable that any sounds directly produced by auroral discharges would reach the ground, and the coincidence of sounds with the visible changes in the auroras conflicts with the necessary propagation time for any sounds from the discharges themselves. Some people speculate that local electrostatic phenomena induced by the auroras might explain the sounds; theories associated with brush discharges seem to fit the reported observations best, although no theory thus far provides a completely satisfactory explanation
There were some other references that I found, but I'll only mention this one, an article from the Oct. 19, 1995 issue of the Alaska Science Forum, and entitled Straining to Hear the Voice of the Aurora. Here's the last part of the article:
The voice of the aurora is still a great mystery. Many people have reported hearing the aurora--in legend and modern times--but scientists haven't yet nailed down the reason.
Tom Hallinan, a professor of geophysics at the Geophysical Institute, has studied the aurora for decades. He said he's heard the aurora and has talked to many others who have.
"There's something going on," Hallinan said of the aurora's whisper. "It's scientifically unreasonable, yet people do hear it."
Hallinan says the thin air of the ionosphere--where the aurora dances from 60 to about 200 miles above the earth's surface--can't carry sound waves. Even if it could, Hallinan says, we're so far away that it would take several minutes for the sound to reach us.
Hallinan suggests a few possible explanations for auroral noise. He said the brain may sense electromagnetic waves from the aurora and somehow convert them to sound. Another theory is that electrical currents induced on the ground by the aurora (which also corrode the trans-Alaska oil pipeline) may create an audible electrical discharge from nearby objects such as spruce trees or buildings.
It's somehow comforting that this part of the aurora borealis remains a mystery. The voice of the aurora will undoubtedly someday be captured on tape and explained, but if I ever hear it, I'll whisper back. Maybe Barron has something to tell us.