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 Institute of Nuclear Physics of the CAS and Institute of Atmospheric Physics of the CAS, in addition to CTU Faculty of Electrical Engineering. The collaborating scientists focused on uncovering the nature of extreme atmospheric phenomena and ionising radiation, discovering the unique properties of lightning discharges. "They are larger in time and space," explains the leader of the scientific team, Ing. Jakub Kákona from the Department of Radioelectronics at the Faculty of Electrical Engineering, 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 ionising 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 here. 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 kilometres. "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 a distance of 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.
Read the full article here.
Vlastnoručně zhotovené měřící vybavení
Nejzásadnějším aspektem výzkumu vědeckého týmu z FEL ČVUT byl nedostatek relevantních přístrojů, který jej „donutil” vyvinout si vybavení vlastní. „Příprava měřící techniky zabrala spoustu času,” prozradil Ing. Jakub Kákona. „Projekt byl oficiálně spuštěn v roce 2016, ale kvůli tomu, že jsme si museli přístroje sestrojit a upravit k obrazu svému sami, první měření proběhlo až v roce 2019.”
Jako první výzkumný tým v Evropě využili vědci z FEL ČVUT tzv. měřící vozidla. Šlo o tři automobily sloužící k přepravě a napájení přístrojů v blízkosti bouřek, a také jako částečná ochrana obsluhy před údery blesku. Podle Ing. Jakuba Kákony šlo o první takto upravená vozidla určená výhradně k vědeckým účelům. „Z USA jistě znáte zábavné pořady o tzv. lovcích bouřek, kteří v autech pronásledují extrémní bouřkové výboje, to má ale často do reality vědeckého počínání daleko.” Autor poznamenává, že právě optimalizování vozidel pro výzkum zabralo velké množství času, protože bylo potřeba vybavit je měřícími přístroji.
I v tom si vědci z FEL ČVUT připisují prvenství. Jako jediní v Evropě vybavili měřící vozy celooblohovými vysokorychlostními kamerami, rádiovými anténami a detektory ionizujícího záření, což do nynějška žádný jiný vědecký tým neudělal. „Dále jsme si sami navrhli tzv. bezpilotní vírník k měření elektrického pole bouřek a instalovali jsme open-source kamery, které jsme vybavili vlastnoručně naprogramovaným softwarem,” doplňuje autor studie, Ing. Jakub Kákona.
Self-made measuring equipment
The most important aspect of the research 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 the 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 with modifications designed exclusively for scientific purposes. "From the USA, you know about the entertaintment 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 were the only ones in Europe to equip the measuring vehicles with full-array high-speed cameras, radio antennas and ionizing 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 Ing. Jakub Kákona, the author of the study.
What will the future bring?
Despite the groundbreaking results, the scientific team from 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 emerged. However, given the observed size variance, it is not unreasonable to assume that it emerges somewhere else before it finally strikes."
The research team wants to get more data from bursts that last longer than originally thought. Jakub Kákona says that analysing longer discharges in the future gives them hope "to have enough time to calculate where the lightning discharge 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 ionising radiation is produced during thunderstorms.
Photography courtesy of Jakub Kákona, FEL: https://drive.google.com/drive/folders/15IOFR-Xx52FE8rCgrck6-i3gciqzYcit?usp=sharing
