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They first recorded the occurrence of a lightning strike – the theory was promptly overthrown

Lightning is the most active and directly observable process on our planet. Since awakening to consciousness, man has admired and feared these discharges, which have long been attributed to the action of supernatural forces, but science has been trying for centuries to describe exactly what happens at such times. but to no avail.

“Actually, it’s very embarrassing,” said lightning researcher Brian Hare, an exhibitor who specializes in lightning. study Co-author. “It’s the most active process on Earth, religions are built on it, and we have no idea how it works.”

The explanation given in the textbook is something like “The formation of lightning can be traced back to friction and fragmentation of water droplets and ice crystals in the clouds, as a result of which the electric charges within the cloud separate. Positive charges accumulate in the upper part of the cloud and negative charges in the lower part,” as you do Wikipedia in the article It was also included. In clouds, larger ice crystals move down, while smaller ones move up, causing electrons to fall off them. As a result, the upper part of the cloud becomes positively charged, the lower part becomes negatively charged, and the resulting electric field is amplified until a massive discharge is finally made.

Lightning over a city – we finally understand how it evolves (Image: Depositphotos)

The only small problem with this is that no one has noticed an electric field in the clouds strong enough for this. “People have been sending balloons, rockets, and planes into thunderclouds for decades, but no one has seen a strong enough electric field,” says Joseph Dwyer, a physicist at the University of New Hampshire and author of the study. The difference is about ten times that, so this model is in no way able to explain what is actually happening. “It’s a real mystery how the process begins,” says Dwyer, who has spent more than two decades of his life researching the formation of lightning.

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They didn’t close their eyes

Now it looks like he’s finally made a breakthrough. One of the difficulties in observing lightning is the fact that the clouds are not transparent. Even the best cameras can’t capture the moments around the onset of lightning, so the only tool researchers have used for a long time has been to send objects equipped with various tools into the storm clouds. However, the problem with this is that the appearance of a foreign body in itself affects the process, for example, it generates sparks that would not otherwise occur.

The solution is presented by radio telescopes capable of detecting radio signals provoked by electrical phenomena. Using these to detect lightning is not a new idea in itself, but the wireless detectors used to monitor lightning so far have taken low-resolution recordings and often only recorded data in two dimensions.

An element of the LOFAR system near Exloo in the Netherlands (Photo: LOFAR/ASTRON)An element of the LOFAR system near Exloo in the Netherlands (Photo: LOFAR/ASTRON)

Dwyer’s idea was to use sensors from the Low Frequency Array (LOFAR), a network of thousands of smaller radio telescopes in the Netherlands. This system is capable of placing the detected signals in three dimensions with an accuracy of one meter, and records data 200 times more than previously used devices.

The researchers were lucky in the summer of 2018: a huge lightning bolt struck the area covered by LOFAR, and the system “watched” the process from start to finish. The analysis of the shocking amount of data has just been completed, and the researchers have also made an amazing simulation of the observation.

In the footsteps of lost electrons

But what did Doerr see? All radio signals come from a part of the cloud with a diameter of about 70 meters, in the depths of the atmospheric phenomenon. This immediately confirmed one of the two most accurate theories of lightning competing so far from the textbook, while at the same time largely disproving the other.

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The essence of the latter is that the process begins within the framework of cosmic radiation through the arrival of particles to the Earth, which collide with the electrons of storm clouds, which leads to the occurrence of an avalanche-like amplifying chain reaction.

The other theory traces the beginning of the process to ice crystals that clump like a swarm in clouds. As a result of turbulent collision, electrons are released from the crystals, as a result of which one end of each crystal becomes positively charged and the other becomes negative. The positive top attracts electrons from surrounding air molecules, creating ionized air bands in an ever-increasing region that attach to the tops of the crystals as a bundle. These are called banners.

Each crystal is associated with a number of this ever-changing stripe. These things then heat the surrounding air, tearing more electrons from the molecules, and imparting an increased voltage to the crystals. Eventually one of the transmitters heats up so much and becomes a good conductor that it becomes a conductor, i.e. a channel capable of draining the energy of the lightning bolt.

“This is exactly what we see in the registry,” says Christopher Stirbka, lead author of the study. Radio pulses multiply exponentially, certainly due to the appearance of the streamers. “Then the avalanche-like propagation stops and the leader appears near them and the lightning itself.” Sterpkas has analyzed a number of similar recordings in recent months, and each has followed a similar pattern to the first.

The results indicate a critical role for ice crystals well are supported There is also data showing that lightning strikes are 10 percent less in the first three months of the Covid pandemic – researchers hypothesize that fewer ice crystals formed in the clouds as the number of small polluting particles decreased.

white spots

Of course, the current study does not have the final say on the issue of lightning. “It is clear that the recordings from LOFAR are of enormous importance,” says Ute Ebert, a physicist at Eindhoven University of Technology who was not involved in the research. Finally, the collected data are of sufficient quality to be able to generate accurate models and simulations that could not be obtained from previous low-resolution data. However, Ebert also draws attention to a weakness. This is because the image doesn’t show the crucial first stage of the process in which ice crystals ionize air, only what happens next. “Where does the first electron come from? How does the discharge with an ice crystal begin?” He asks the question.

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Based on the results, most researchers have abandoned the cosmic radiation theory, but the high-energy particles that appear can play a role in the formation of lightning by forming the first free electrons, which then lead to the formation of the first streamers. It is also debatable how exactly the banners will become leaders.

Dwyer is confident that they will soon be able to see this matter more clearly, too. “We try to notice the first little sparks that explode from the crystals, and thus initially capture the formation process,” he says.

Even if that worked, the researchers wouldn’t be left without a job. “We don’t know how it spreads and grows,” Hare only lists key unanswered questions. “We don’t know how it relates to the soil.”

Despite many ambiguities, all experts agree that the LOFAR results represent a huge, long overdue step forward in understanding a phenomenon that has been researched for centuries. Perhaps the point won’t be far when humanity can finally say that we have a theory that, even omitting Zeus and his companions from the story, could provide a full explanation of how lightning works.

(Quanta Magazine)