In a fraction of a second, lightning heats the air around it to incredible temperatures-as hot as 54,000 ☏ (30,000 ☌). We may see several strokes using the same path, giving the lightning bolt a flickering appearance, before the electrical discharge is complete.Ĭlick for larger animated image! What causes thunder? The channels connect and we see the lightning stroke. Although this phase of a lightning strike is too rapid for human eyes, this slow-motion video shows it happening.Īs the negative charge gets close to the ground, a positive charge, called a streamer, reaches up to meet the negative charge. A "stepped leader" of negative charge descends from the cloud seeking out a path toward the ground. These positive charges move up into the tallest objects like trees, telephone poles, and houses. Often lightning occurs between clouds or inside a cloud.īut the lightning we usually care about most is the lightning that goes from clouds to ground-because that's us!Īs the storm moves over the ground, the strong negative charge in the cloud attracts positive charges in the ground. It looks for the closest and easiest path to release its charge. The electric field "looks" for a doorknob. How does the lightning "know" where to discharge-or strike? When the strength of the charge overpowers the insulating properties of the atmosphere, Z-Z-Z-ZAP! Lightning happens. These electrical fields become incredibly strong, with the atmosphere acting as an insulator between them in the cloud. It's a little more complicated than that, but what results is a cloud with a negatively charged bottom and a positively charged top. Where the ice going down meets the water coming up, electrons are stripped off. Meanwhile, downdrafts in the cloud push ice and hail down from the top of the cloud. Water droplets in the bottom part of the cloud are caught in the updrafts and lifted to great heights where the much colder atmosphere freezes them. Winds inside the cloud are very turbulent. Researchers continue to develop images from the data and hope to learn more about how often fast negative breakdown events occur and what fraction of them can initiate an actual lightning flash.Lightning begins as static charges in a rain cloud. An array of ground-based antennas picked up the radio waves, which then allowed researchers to create a highly detailed image of the radio sources and identify this unusual phenomenon. In collaboration with a lightning research team from New Mexico Institute of Mining and Technology, the researchers documented fast negative breakdown in a Florida lightning storm at Kennedy Space Center using radio waves originating deep inside the storm clouds. "These findings indicate that lightning creation within a cloud might be more bidirectional than we originally thought," said Julia Tilles, a doctoral candidate in the UNH Space Science Center. Ultimately, this provides scientists with a new view of what's possible inside a storm cloud. However, the newly reported observation of fast negative breakdown shows that an upward pathway - going in the opposite direction and just as fast - can be created in a thundercloud, indicating there's another way to start electricity in the air. The pathway forms at one-fifth the speed of light and can trigger lightning. Fast positive breakdown involves the downward development of a pathway in the cloud, moving from the positive charge at the top of the cloud to the negative charge in the middle of the cloud. Recently, the problem of lightning initiation seemed to be solved with the discovery of "fast positive breakdown" of air, which matched the theory long held by lightning researchers.
Their finding, published in the journal Nature Communications, is another step toward answering the question of how lightning begins.
The process was totally unexpected and gives us more insight into how lightning starts and spreads."
"Despite over 250 years of research, how lightning begins is still a mystery. "This is the first time fast negative breakdown has ever been observed, so it's very exciting," said Ningyu Liu, professor of physics.
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