A high-speed photograph taken just 1/25,000th of a second before lightning struck one of the buildings revealed unprecedented details about how lightning rods work.
Rare high-speed photos of lightning showing connections to nearby lightning rods help scientists understand how these devices compete to attract lightning strikes and keep buildings safe from damage.
Made possible by a combination of well-planned efforts and sheer luck, this image was captured during a thunderstorm. Sao Jose dos Campos, Brazil, It was taken with a high-speed camera by physicist Marcelo Zaba and PhD student Diego Ramón, researchers at Brazil’s National Institute for Space Research (INPE).
A lightning rod emits an upward discharge and attracts lightning
According to researchers who published their analysis in Geophysical Research Letter, the image shows negatively charged lightning approaching the ground at 370 kilometers per second. When lightning reaches about 30 meters above the ground, “Lightning rods and tall objects on top of nearby buildings competed to create upward positive discharges and connect with downward impacts.” Saba explained release From FAPESP.
“The final pre-connection image was taken 25 thousandths of a second before a lightning strike hit one of the buildings,” Saba added.
The researchers used cameras that captured 40,000 frames per second. High-speed equipment allowed researchers to assess the impact of this kind of downloads, especially when appropriate protective measures were not in place. In this particular case, a failed installation exposed the area and caused considerable damage under the influence of a 30,000 amp discharge.
“A staggering total of 31 lightning precursor channels (called leaders) were launched from nearby buildings in an attempt to intercept the descending negative leader.”
lightning, electric properties
Press releases estimate that, on average, only 20% of lightning strikes hit the ground and the rest are trapped in clouds. Almost all lightning strikes that strike the ground are discharges from the cloud to the ground. Upward discharges also occur, but are rare. Lightning can also be classified as negative or positive based on the charge transferred to the ground.
“A lightning strike can reach a length of 100 km and carry a current of 30,000 amperes, which is equivalent to the current used by 30,000 100-watt light bulbs. The temperature of a typical lightning strike is 30,000 °C, five times the surface temperature of the sun,” Saba explains.
A lightning strike has a characteristic zigzag shape because electric charges try to follow the path of least resistance to the ground instead of the most direct path. “Its trajectory is determined by various electrical properties of the non-homogeneous atmosphere.”
Rather than repel or attract such discharges, lightning rods simply provide lightning with an easy and safe path to the ground, according to the team.
Saba began systematically studying lightning with high-speed cameras in 2003 and has since created the world’s largest collection of high-speed lightning video, according to the statement.