What does thunder look like? Scientists create first-ever visual depiction

Scientists have finally formed visual imagery of thunder for the first time by capturing sounds waves that are created when artificially causing lightning. The researchers from Southwest Research Institute (SwRI) will be presenting the first of the images at an upcoming meeting of American and Canadian geophysical societies that will take place in Montreal, Canada from May 3rd, 2015 to May, 7th.

‘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.’

Despite the fact that people view it as a flashing bolt, lightning actually begins as quite a complex course containing electrostatic charges tossing around in storm clouds. These charges ignite step leaders, which are splitting veins of electricity spreading down that subsequently lead to a central discharge channel. That channel then opens up a path to instantly return strokes, which formulate lightning flash as we see it. By revising the acoustic power discharged from various portions of the lightning channel, scientists can learn more about the background of thunder in addition to the energetic progressions related to lightning.

‘Thunder and lightning are fascinating, wild, and unpredictable,’ said Dayeh. “Because of their erratic nature, the phenomena are best studied using triggered events.’ This method consists of ejecting a small rocket sprawling a grounded copper wire into thunderclouds. The copper wire delivers a conductive channel and produces a foreseeable pathway for lightning, allowing researchers to concentrate their instruments accurately and accomplish repeatable trials near the discharge channel. Utilizing the SwRI internal research subsidy, Dayeh led a proof-of-concept trial to carbon copy the acoustic mark of thunder. SwRI led experiments at the International Center for Lightning Research and Testing at the University of Florida, Gainesville, gaining the benefit of the state’s entitlement to the greatest lightning strikes per year in the United States.

Dayeh created an excellent, refined array of microphones to research the acoustic mark of thunder. Fifteen microphones, spaced out one meter apart, stood side by side 95 meters away from the rocket launch pad where the generated lightning struck. To duplicate the vertical outline of the bolt, he utilized post-signal handling methods and guiding augmentation of the data indicators captured by the microphone array.

‘At first I thought the experiment didn’t work,” stated 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.’

Though, when Dayeh observed the various sound occurrence bands, he noticed that the images emptied up at higher rates. The practice exposed a distinct mark of thunder produced by the lightning strike. Forthcoming trials could allow researchers to study the possible acoustic marks of present pulses, step leader branches, and release channel zigzags self-sufficiently.

Highlights of this research will be discussed at a press conference being held on May 5 at 11:30 a.m. EDT, at the 2015 Joint Assembly at the Palais des congrès de Montréal, Canada. Dayeh collaborated with groups from Florida Institue of Technology, University of Florida, and the University of New Hampshire. The American Geophysical Unions, the Geological Association of Canada, Canadian Geophysical Union, and the Mineralogical Association of Canada are amongst the organizations sponsoring the event.

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