Why do the rays split and flash? It seems like a question asked by a child, but this is the subject of a study by a team from the National Institute for Space Research (Inpe), with the collaboration of researchers from the USA, England and South Africa, now published in the journal Scientific Reports.
To understand how lightning is formed, Inpe’s Atmospheric Electricity Group (Elat) recorded images of slow-motion rays (a process called super slow motion), capturing the exact moment when more than 200 upward energy discharges (this that is, from the earth to the clouds) they form, tear the sky, fork and shine during summer storms in São Paulo and South Dakota (USA), between 2008 and 2019.
To do this, they used a combination of high-speed digital and video cameras, capable of recording between 10,000 and 40,000 images per second. The researchers also counted on electric field and luminosity meters and an ultra-high speed camera, which records one hundred thousand images per second.
“Rising rays generally come from the tip of a tower or lightning rod from a tall building as a result of the disturbance of the storm’s electric field, caused by a descending ray that occurs at a distance of up to 60 kilometers,” he explained to the Agency FAPESP the project coordinator, space geophysicist Marcelo Magalhães Fares Saba.
Ascending rays are less common than descending rays (those that come out of the clouds towards the ground, and already studied by the same researchers previously). In more than ten years of observations, only light structure formations were observed in only three ascending rays (all in the USA) with a positive charge, that is, that propagates towards the base of the cloud.
“The advantage of registering images of these rays upwards is that it is possible to visualize the entire trajectory of the positive leaders, from the ground to the base of the cloud. Once inside the cloud, it is no longer possible to observe the discharge ”, explained the researcher, noting that, at the end of the three flashing structures observed, there was another, more tenuous discharge, similar to a brush.