Scientists Image Thunder for the First Time Ever

For the first time ever, scientists have captured "images" of thunder. They've visually captured sound waves created by artificially triggered lightning.

"Lightning strikes the Earth more than four million times a day, yet the physics behind this violent process remain poorly understood," said Maher Dayeh, one of the researchers, in a news release. "While we understand the general mechanics of thunder generation, it's not particularly clear which physical processes of the lightning discharge contribute to the thunder we wear. A listener perceives thunder largely based upon the distance from lightning. From nearby, thunder has a sharp, cracking sound. From farther away, it has a longer-lasting, rumbling nature."

Although people see lightning as a flashing bolt, it first begins as a complex process of electrostatic charges churning around in storm clouds. These charges initiate step leaders, branching veins of electricity propagating down, which subsequently lead to a main discharge channel. That channel opens a path to nearly instantaneous return strokes, which form the lightning flash as we see it.

 In this case, the researchers studied the acoustic power that radiated from different portions of the lightning channel. This, in turn, told the researchers a bit more about the origins of thunder as well as the energetic processes associated with lightning.

"Thunder and lightning are fascinating, wild and unpredictable," said Dayeh. "Because of their erratic nature, the phenomena are best studied using triggered events."

The researchers triggered lightning by launching a small rocket trailing a grounded copper wire into thunderclouds. This allowed the scientists to focus their instruments on the discharge channel. The researchers looked at the different sound frequency bands and found that at higher frequencies, there were clear images; in other words, the scientists managed to image the acoustics of thunder.

"At first I thought the experiment didn't work," said Dayeh. "The initial constructed images looked like a colorful piece of modern art that you could hang over your fireplace. But you couldn't see the detailed sound signature of lightning in the acoustic data."

When the researchers looked at the different sound frequency bands, though, they found the images cleared up at higher frequencies.

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