The result of the research is all the more significant because it is the first such finding in Europe. The CRREAT (Centre of Cosmic Rays and Radiation Events in the Atmosphere) project involved the Faculty of Electrical Engineering of CTU, the Nuclear Physics Institute of the CAS, and the Institute of Atmospheric Physics of the CAS. The collaborating scientists focused on uncovering the nature of extreme atmospheric phenomena and ionizing radiation, discovering the unique properties of lightning discharges. "They are more dimensional in time and space," explains the leader of the scientific team, Ing. Jakub Kákona from the Department of Radio Electronics at the Faculty of Electrical Engineering of CTU, and adds: "Further research needs to be done on a scale other than the local one as before."
The largest and longest-lasting lightning in Central Europe
The scientific team led by Ing. Jakub Kákona published in January 2023 a groundbreaking paper entitled In situ ground-based mobile measurement of lightning events above central Europe, describing the advantages of the equipment used for ground-based measurement of thunderstorm events in central Europe. The main objective of the investigation was to verify whether lightning is (un)related to ionizing radiation. The observation of the temporal and spatial extent of lightning was added as a by-product, as it were, by "accident", yet the researchers collected interesting data. Part of the research involved comparing the results with data published in foreign media.
To measure the size of the lightning, the researchers used the public detection network Blitzortung.org, which determines the location of the lightning discharge with an accuracy of kilometers. "Although our detectors showed that one of the lightning bolts passed almost directly over our measuring vehicle, the closest lightning bolt detected by Blitzortung.org was 70 to 80 km away," says Ing. Jakub Kákona in the article. "From this, we infer that the lightning was more than 80 km long, or that the synchronous discharge occurred at a distance of 80 km."
This is the largest lightning discharge detected so far by the method of ground measurement of storm phenomena in Central Europe. Elsewhere in the world (typically in the USA), many times larger lightning bolts have been detected thanks to satellite imagery. In 2022, the CAS reported a lightning bolt over the southern tip of the United States that traveled 768 kilometers inside a storm cloud, beating the last record holder from southern Brazil by some 60 kilometers.
Measurements of the duration of the discharge also yielded interesting results. Measured durations are typically in the order of hundreds of milliseconds, with shorter lightning events being rare. "The median duration of a lightning discharge is 0.52 s. This is significantly higher than the values reported in other studies," adds Jakub Kákona. Foreign publications report a range of median discharge duration from 0.20 to 0.35 s, with the Spanish record holder being a 2017 lightning bolt lasting 2.39 s (1.80 s in winter). The maximum duration of lightning can be as short as a few seconds, which, according to Jakub Kákona, is neither frequent nor exceptional.
You can read the full article here.
Self-made measuring equipment
The most important aspect of the research team from FEL CTU was the lack of relevant instruments, which "forced" them to develop their own equipment. "The preparation of the measuring equipment took a lot of time," revealed Ing. Jakub Kákona. "The project was officially launched in 2016, but due to the fact that we had to build and adapt the instruments ourselves, the first measurements were not taken until 2019."
As the first research team in Europe, scientists from FEL CTU used so-called measuring vehicles. These were three vehicles used to transport and power instruments in the vicinity of storms, and also as partial protection for the operator from lightning strikes. According to Ing. Jakub Kákona, these were the first vehicles so modified and designed exclusively for scientific purposes. "From the USA, you know about the funny programmes about so-called storm chasers who chase extreme storm discharges in cars, but this is often far from the reality of scientific activity." The author notes that it was optimising the vehicles for research that took a great deal of time, as they needed to be equipped with measuring instruments.
Scientists from FEL CTU are also the first in this field. They are the only ones in Europe to equip the measuring vehicles with full-circle high-speed cameras, radio antennas and ionising radiation detectors, which no other scientific team has done so far. "We also designed our own so-called unmanned vortex vehicle to measure the electric field of storms and installed open-source cameras equipped with our own software," adds study author Ing. Jakub Kákona
What will the future bring?
Despite the groundbreaking results, the scientific team from the FEL CTU and the Academy of Sciences of the Czech Republic has still not managed to find out what actually triggers lightning. The failure to achieve this goal is attributed by the team leader, Ing. Jakub Kákona, to insufficient equipment. "With three measuring vehicles, we simply could not cover the whole region at once to find out exactly where the lightning started. However, given the observed size variance, it is not unreasonable to assume that it starts somewhere else before it finally strikes."
The research team wants to get more data from bursts that last longer than originally thought. In the words of Jakub Kákona, analysis of longer bursts in the future gives them hope "to have enough time to calculate where the lightning burst will actually start and what its strength is likely to be."
Related to this is a possible breakthrough in the implementation of safety measures to prevent damage (typically in air transport, for example) and in the design of lightning rods, which are still installed locally on the tops of tall buildings. It will also have an impact on existing storm forecasting models. The team around Ing. Jakub Kákona is going to examine the lightning discharges using antennas and cameras at the same time to determine the actual size of the lightning, and also to make a 3D lightning model. They believe that these measurements will in the future contribute to a better understanding of where and when ionizing radiation is produced during thunderstorms.
Author of the photos: Jakub Kákona, FEE CTU