With a high-speed camera and the luck of being in the right place at the right time, physicist Marcelo Saba, a researcher at Brazil's National Space Research Institute (INPE), and PhD candidate Diego Rhamon obtained a unique image of lightning strikes showing details of the connections to nearby buildings.
The image is so special that it appeared on the cover of the 28 December 2022 issue of Geophysical Research Letters (GRL) – one of the most important scientific journals in the field –, which featured an article with Saba as first author. Saba's research on this topic was supported by FAPESP.
"The image was captured on a summer evening in São José dos Campos [in São Paulo state] while a negatively charged lightning bolt was nearing the ground at 370 km per second. When it was a few dozen meters from ground level, lightning rods and tall objects on the tops of nearby buildings produced positive upward discharges, competing to connect to the downward strike. The final image prior to the connection was obtained 25 thousandths of a second before the lightning hit one of the buildings," Saba said. This is the spectacular image featured on the cover of the journal.
He used a camera that takes 40,000 frames per second. When the video is played back in slow motion, it shows how lightning discharges behave and also how dangerous they can be if the protection system is not properly installed: although there are more than 30 lightning rods in the vicinity, the strike connected not to them but to a smokestack on top of one of the buildings. "A flaw in the installation left the area unprotected. The impact of a 30,000-amp discharge did enormous damage," he said.
On average, 20% of all lightning strikes involve an exchange of electrical discharges between clouds and the ground. The other 80% occur inside clouds. Almost all strikes that touch the soil are cloud-to-ground discharges. Upward strikes also occur but are rare and start at the top of tall structures such as…