A team of scientists from the University of New Hampshire Space Science Center, the Langmuir Laboratory for Atmospheric Research, Earth Networks and NASA’s John F. Kennedy Space Center has documented a unique event — called ‘fast negative breakdown’ — that occurs in clouds before a lightning flash happens.
Tilles et al observed a possible new way that lightning forms called fast negative breakdown.
Recently, the problem of lightning initiation seemed to be solved with the discovery of fast positive breakdown, which matched the theory long held by lightning researchers.
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. The pathway forms at one-fifth the speed of light and can trigger lightning.
However, the 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.
Ultimately, this provides scientists with a new view of what’s possible inside a storm cloud.
“These findings indicate that lightning creation within a cloud might be more bidirectional than we originally thought,” said study co-lead author Julia Tilles, a doctoral candidate in the University of New Hampshire Space Science Center.
Tilles and colleagues documented fast negative breakdown in a Florida lightning storm at NASA’s Kennedy Space Center using radio waves originating deep inside the storm clouds.
An array of ground-based antennas picked up the radio waves, which then allowed the researchers to create a highly detailed image of the radio sources and identify this unusual phenomenon.
“This is the first time fast negative breakdown has ever been observed, so it’s very exciting,” said study co-lead author Professor Ningyu Liu, also from the University of New Hampshire Space Science Center.
“Despite over 250 years of research, how lightning begins is still a mystery. The process was totally unexpected and gives us more insight into how lightning starts and spreads.”
The findings appear in the journal Nature Communications.
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Julia N. Tilles et al. 2019. Fast negative breakdown in thunderstorms. Nature Communications 10, article number: 1648; doi: 10.1038/s41467-019-09621-z
