Studying downward terrestrial gamma-ray flashes during a winter thunderstorm

Studying downward terrestrial gamma-ray flashes during a winter thunderstorm
Locations of the detectors in the Kashiwazaki-Kariwa Nuclear Power Station. Orange circles show detectors A–C, blue circles monitoring posts (MPs), and the green star the estimated position where the TGF took place. The size of the blue circles indicates the dose of the present TGF. Red crosses and dashed-line ellipses show the positions of lightning discharges and their errors reported by JLDN, respectively. The numbers 1–3 indicate the time order of these discharges. Detector B and MP6 are installed co-spatial. MP8 data was unavailable in the present study. Credit: Wada et al.

Lightning is a unique and fascinating phenomenon that has been studied for centuries. Although we now have a better understanding of this naturally occurring spectacle, many of its secrets are yet to be uncovered.

For several decades, researchers have been aware that lightning strikes are accompanied by flashes, a type of electromagnetic radiation. These flashes can be downward-facing (i.e. directed to the ground) or upward-facing (i.e. directed upward into space).

Most past studies have observed these flashes from space, and have thus primarily focused on upward-facing gamma-ray flashes. In an intriguing new study, a research team at the University of Tokyo and other Japanese Universities have investigated the downward gamma-ray emissions that take place during thunderstorms for the very first time. Their paper, published in Physical Review Letters, confirms that downward-facing flashes are the same as those directed upward, and that they are not harmful to people on Earth.

"Since 1990s, intense gamma-ray emissions called terrestrial gamma-ray flashes (TGFs) have been observed by in-orbit satellites coincident with lightning discharges," Yuuki Wada, one of the researchers who carried out the study, told Phys.org. "While they are usually directed from thunderstorms into space, some of them, called downward TGFs, go to the ground. However, it was difficult to measure their on-ground gamma-ray fluxes because downward TGFs take place closer to gamma-ray detectors and saturate them."

In their study, Wada and his colleagues studied that occurred on the 24th of November 2017 during a heavy winter thunderstorm. On that date, radiation detectors installed at sea level at the Kashiwazaki-Kariwa Nuclear Power Station in Japan detected a strong burst of gamma-rays, which coincided with a powerful lightning discharge. By studying the data collected by these detectors, the researchers gathered the very first observations of lightning-associated TGFs directed to the ground.

"We used two types of radiation detectors," Wada explained. "One has better timing resolution and sensitivity to gamma rays, but could be easily saturated by high fluxes of downward TGFs. It is used to confirm the occurrence of downward TGFs. The other is gas dosimeters operated by Tokyo Electric Power Company Holdings. These have less timing resolution than the former, but stand much higher gamma-ray rates."

Remarkably, Wada and his colleagues are the first to successfully measure on-ground radiation doses of downward-facing TGFs. Moreover, by measuring the rays using multiple gas dosimeters, they achieved high-quality data at multiple observation points.

The researchers were able to ascertain the accuracy of Monte-Carlo simulations they had created, which were comparable to the high-quality data. This ultimately allowed them to uncover key physical features of downward-facing TGFs, including their origin within the thundercloud.

"TGFs are thought to originate from energetic electrons accelerating in lightning," Wada said. "However, the dense atmosphere on Earth prevents electrons from getting relativistic energy. We are convinced that observations of downward TGFs will play an important role to finding answers to this question, because they can be observed by multiple and closer on-ground apparatus."

The observations gathered by Wada and his colleagues have numerous interesting implications. Firstly, their work confirms that downward TGFs are intrinsically the same phenomenon as upward TGFs that were previously observed from space.

Their results also suggest that TGFs are fairly safe for people on the ground in the area where a thunderstorm is taking place. On the other hand, the location within a cloud where the TFG originates from might not be very safe.

In addition to broadening our understanding of gamma-ray bursts that take place during thunderstorms, the study carried out by this team of researchers unveiled some limitations of detectors that are commonly used to collect data during lightning storms. This could inform the development of new tools to improve detection, ultimately leading to the collection of higher-quality of data using radiation monitors.

"Our group is now making a new radiation-monitoring network at Kanazawa city in Japan, which is famous for powerful and frequent winter lightning," Teru Enoto, another researcher involved in the study, told Phys.org. "This network will provide us much more number of high-energy events at lightning, similar to this event. We are also collaborating with citizen supporters to cover a wider area with portable radiation detectors. We are very excited to reveal mysteries of via our citizen-supporting and open-science approach."


Explore further

Researchers connect lightning with gamma-ray phenomena in clouds

More information: Y. Wada et al. Downward Terrestrial Gamma-Ray Flash Observed in a Winter Thunderstorm, Physical Review Letters (2019). DOI: 10.1103/PhysRevLett.123.061103

www.u-tokyo.ac.jp/focus/en/art … les/z0508_00054.html

Journal information: Physical Review Letters

© 2019 Science X Network

Citation: Studying downward terrestrial gamma-ray flashes during a winter thunderstorm (2019, August 27) retrieved 18 September 2019 from https://phys.org/news/2019-08-downward-terrestrial-gamma-ray-winter-thunderstorm.html
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Aug 27, 2019
So ...even more radiation exposure for people in planes? Has there been no testing of radiation in planes that fly thru or very near thunderstorms?

Aug 27, 2019
DE, you asked? great!

this is what you will need to do
if you are already part of a research team investigating these problems?
be sure to provide links to your groups released papers

if you are not? u would suggest you contact the US Meteorological & the US Geological Survey websites for material & sources

then you will know which of yout concerns are not being met by contemporary research projects

The info you collect will assist you in figuring out a rough table of probable costs. the resources such as laboratory aircraft salaries of scientists, aircrews supporting personnel

finally you are prepared to approach your congressperson to get their support for this needed research

get all your ducks in a row & set'em free!

please post updated progress reports
thanks DE

Aug 27, 2019
Their paper, published in Physical Review Letters, confirms that downward-facing flashes are the same as those directed upward, and that they are not harmful to people on Earth.
Perhaps you should read the article more carefully, @Darth.

Aug 28, 2019
Their paper, published in Physical Review Letters, confirms that downward-facing flashes are the same as those directed upward, and that they are not harmful to people on Earth.
Perhaps you should read the article more carefully, @Darth.


I did. You do realize that planes fly much closer to the source of the gamma ray's right? being in the same clouds and all? Planes aren't protected by the dense air near the surface and so are exposed to radiation levels much higher than those of people on the surface under normal flying altitudes even without clouds.

The question was if there was any testing done on planes flying thru or very near thunderstorms that are producing these gamma ray flashes.

Are they too highly directional and you must be directly under them (basically struck by lightning to be in the danger zone). Or is the less dense air enough to be exposed if within a few thousand feet of any regardless of where you are.

Aug 28, 2019
I did. You do realize that planes fly much closer to the source of the gamma ray's right? being in the same clouds and all? Planes aren't protected by the dense air near the surface and so are exposed to radiation levels much higher than those of people on the surface under normal flying altitudes even without clouds.

It really doesn't matter. Being near enough to one of these would be extremely rare and the energy released from these bursts is only 40 mSv. People who undergo radiation therapy receive doses of about 1 Sv, 25 times the amount one of these bursts release. About 8 Sv is enough to outright kill you. An increased cancer risk is basically non-existent; that would require long term exposure, not just a few milliseconds.

The question was if there was any testing done on planes flying thru or very near thunderstorms that are producing these gamma ray flashes.

Planes generally fly around or over thunderstorms, but yes there have been several studies on this.

Aug 28, 2019
ok, was just wondering since the article stated that it may not be safe in the cloud, but if the radiation levels are so little, why even make the comment?

I wasn't expecting there to be a cancer risk for passengers and the like. Was more along the lines of exposure to people who work on the plane so they're potentially seeing stormy flights multiple times a year. But that was under the assumption that the burst produced something that was actually dangerous up in the clouds as suggested.


Aug 28, 2019
"... ok, was just wondering since the article stated that it may not be safe in the cloud, but if the radiation levels are so little, why even make the comment? ..."

because radiation damage is accumulative
until vaping & hotpoting, tobacco & marijuana use took time to trigger emphysema & cancers
didn't make the dangers less real

no matter the money the tobacco lobby paid deniers to declaim the science

the danger (usually) from known radiation, will not be from a single strike...probably
it is over a span of time, that a multitude of random radiation strikes could cause noticeable damage

& how do you figure in secondary & tertiary cascades of particles as the original cosmic ray billiards through your shielding?

this would delve into the complexity of the uncertainty principle & even worse...
actuarial statistical estimations

try reading those tables if you are suffering from insomnia
puts me out like a light...
guaranteed!

Aug 28, 2019
@Darth, no one sane flies any aircraft through the middle of a giant cumulonimbus; certainly not a passenger plane. It's one of the most dangerous things you can do; right up above a high-speed low-level run. Planes are strong, but not that strong; the updrafts and downdrafts can destroy an aircraft, and any passengers subjected to Level 4 turbulence (Extreme) are likely to be injured by the seatbelts. In addition, it causes the pilot to lose control of the aircraft for varying periods of time. This level of turbulence is common inside developed cumulonimbus clouds.

Since this is the area of a cumulonimbus where the charge concentration rises to a level to create lightning, it's very unlikely that a passenger plane would fly through it; certainly never by choice, and thunderheads are pretty easy to spot and avoid from a long way away.
[contd]

Aug 28, 2019
[contd]
So for that reason, it's very improbable that a plane would be near enough to the site where the gamma rays are generated to get more than a minor dose; not much compared to the additional cosmic ray dose that goes with flying around up near the stratosphere, which most long-range passenger aircraft do as a matter of course.

I'm still a little doubtful about a strong concentrated gamma source in thunderheads; I think this is more likely a diffuse source, running along the path of the lightning bolt and forming the occasional radionuclide along that path.

The atmosphere doesn't provide much shielding against gamma rays; they're the most powerful of light rays, and generally pass through most material objects without obstruction. The main protection is to be far enough from the source for them to be attenuated by the inverse square law. And if you don't actually fly through the middle of the thunderhead, then you are miles off.
[contd]

Aug 28, 2019
[contd]
In short, I would expect that anyone close enough to receive even enough gamma to significantly increase their risk of cancer would be in so much trouble that cancer in twenty years would be the least of their worries. It would be like worrying about whether you're going to get cancer later when you're experimenting with cyanide.

Aug 28, 2019
Gamma rays created in nature by electric discharge, this is likely the origin of cosmic GRB's.

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