Why lightning often strikes twice: Study reveals needle-like structures in positively charged lightning leaders

phys.org | 4/10/2019 | Staff
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In contrast to popular belief, lightning often does strike twice, but the reason why a lightning channel is 'reused' has remained a mystery. Now, an international research team led by the University of Groningen has used the LOFAR radio telescope to study the development of lightning flashes in unprecedented detail. The results were published on 18 April in the science journal Nature.

The team used the LOFAR radio telescope to study the development of lightning flashes in unprecedented detail. Their work reveals that the negative charges inside a thundercloud are not discharged all in a single flash, but are in part stored alongside the leader channel at interruptions, at structures that the researchers call needles. This may cause a repeated discharge to the ground.

Finding - Contrast - Picture - Charge - Plasma

"This finding is in sharp contrast to the present picture, in which the charge flows along plasma channels directly from one part of the cloud to another, or to the ground," explains Olaf Scholten, professor of physics at the KVI-CART institute of the University of Groningen. It was never possible to observe the needles before the "supreme capabilities" of LOFAR, adds his colleague Dr. Brian Hare, first author of the paper. "These needles can have a length of 100 meters and a diameter of less than five meters, and are too small and too short-lived for other lightning detections systems."

Low-frequency array (LOFAR) is a Dutch radio telescope consisting of thousands of simple antennas spread over Northern Europe. These antennas are connected with a central computer through fiber-optic cables, which means that they can operate as a single entity. LOFAR is developed primarily for radio astronomy observations, but the frequency range of the antennas also makes it suitable for lightning research, as discharges produce bursts in the VHF (very high frequency) radio band.

Lightning - Observations - Scientists

For the present lightning observations, the scientists...
(Excerpt) Read more at: phys.org
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