DURHAM — A researcher from the University of New Hampshire is helping scientists understand how lightning can strike the same object twice.
Joseph Dwyer, a physics professor at UNH’s Space Science Center, says a low-frequency array Dutch radio telescope with thousands of antennas spread over Northern Europe is providing new information to scientists and enthusiasts by capturing images of how lightning flashes work — in ways that high speed cameras have not been able to do in the past.
These new observations show that lightning has structures called needles. Because these needles can draw an electrical current away from the channel, they can affect how that channel behaves, and this explains why lightning stops striking an object after making contact but can then re-strike it moments later, Dwyer said.
“These needles are new. Nobody really knew they were there,” Dwyer said.
The 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 detection systems.
The finding of needles is in sharp contrast to the present picture of how lightning has been envisioned, in which the charge flows along plasma channels directly from one part of the cloud to another, or to the ground.
It is believed that lightning occurs when strong updrafts generate a kind of static electricity in large cumulonimbus clouds. Parts of the cloud become positively charged and other parts are negatively charged.
Dwyer said that, until now, there wasn’t a good consensus on what positively charged lightning branches look like.
Dwyer said he helped support the research by traveling to the Netherlands to help interpret the data for Brian Hare and Olaf Scholten, the two lead authors on a new study published this week in the science journal Nature. Dwyer is credited as the third author on the study.
Dwyer, who has been studying lightning since 2001, said even though people typically envision Benjamin Franklin when they think about scientists researching lightning, there is still much to be learned.
“Most people are surprised to find out we don’t understand lightning very well,” Dwyer said.
Lightning typically strikes tall objects such as trees or skyscrapers but can hit the ground in an open field, so Dwyer said people should be extra cautious with lightning and stay inside during thunderstorms.