LONDON: For the first time, scientists have imaged thunder, visually capturing the sound waves created by artificially triggered lightning. Researchers from Southwest Research Institute (SwRI) are presenting the first images at a joint meeting of American and Canadian geophysical societies in Montreal, Canada, May 3-7.
“Lightning strikes the Earth more than 4 million times a day, yet the physics behind this violent process remain poorly understood,” said Dr. Maher A. Dayeh, a research scientist in the SwRI Space Science and Engineering Division. “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 hear. 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 it as a flashing bolt, lightning 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. By studying the acoustic power radiated from different portions of the lightning channel, researchers can learn more about the origins of thunder as well as the energetic processes associated with lightning.
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