DURHAM, N.H.—Lightning, for all its breathtaking and fearsome beauty, remains an incredibly mysterious force of nature. Researchers at the University of New Hampshire have discovered a key piece of evidence that has eluded scientists since the days of Ben Franklin’s kite experiment—how lightning actually begins within a storm cloud. The research could fundamentally shift the future of lightning research and ultimately help protect humans and infrastructure from lightning strikes.
“This is huge,” said Chris Sterpka, a doctoral student. “This is the first time we can actually see lightning initiation in three dimensions and on such a small scale—these new data offer an increase in timing precision and accuracy over previous studies, which allowed us to image lighting with more detail.”
In the study, recently published in the journal Geophysical Research Letters, scientists turned to a large array of radio telescopes (called Low Frequency Array, or LOFAR) located in the Netherlands to pick up radio waves generated from lightning. A large lightning event recorded by LOFAR in 2018 caught the eye of some scientists. Sorting through the enormous amount of data, they discovered detailed images of the exact moment when lightning may have started. After months of piecing together a three-dimensional map using radio waves, the team grew increasingly excited to conclude that the sources of lightning are indeed the streamers, or a branching development of tiny spark-like discharges. Their finding supports one of two competing theories, the hydrometeor initiation theory, a process that lightning is formed on a subatomic level by the condensation of atmospheric water vapor inside rain clouds.
“This study really sheds light on how the majority of lightning flashes are initiated,” said Ningyu Liu, professor of physics and a co-author on the paper. “Previous research using small radio sensor arrays has helped us to study the electrical breakdown at the start of large lightning events that generate strong radio signals, but the LOFAR radio telescopes are much more powerful, allowing us to obtain details of lightning initiation starting with weak radio events.”
Within the lightning science community, there have been two major theories on how lightning begins: either by cosmic rays from outer space that enhance the electrical field within the clouds, or by a series of subatomic processes that cause electrons within the cloud to form streamers, which are filamentous cold plasma. The problem is that it is difficult to see inside a storm cloud to find out which theory holds weight; cameras flown into clouds haven’t proven very successful, so scientists turned to the radio telescopes used in this research.
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Journal
Geophysical Research Letters