Lightning, with a chance of antimatter

November 22, 2017, Kyoto University
A Kyoto University-based team has unraveled the mystery of gamma-ray emission cascades caused by lightning strikes. Credit: Kyoto University/Teruaki Enoto

A storm system approaches: the sky darkens, and the low rumble of thunder echoes from the horizon. Then without warning... Flash! Crash!—lightning has struck.

This scene, while familiar to anyone and repeated constantly across the planet, is not without a feeling of mystery. But now that mystery has deepened, with the discovery that can result in matter-antimatter annihilation.

In a collaborative study appearing in Nature, researchers from Japan describe how from lightning react with the air to produce radioisotopes and even positrons—the antimatter equivalent of electrons.

"We already knew that thunderclouds and lightning emit gamma rays, and hypothesized that they would react in some way with the nuclei of environmental elements in the atmosphere," explains Teruaki Enoto from Kyoto University, who leads the project.

"In winter, Japan's western coastal area is ideal for observing powerful lightning and thunderstorms. So, in 2015 we started building a series of small gamma-ray detectors, and placed them in various locations along the coast."

But then the team ran into funding problems. To continue their work, and in part to reach out to a wide audience of potentially interested members of the public as quickly as possible, they turned to the internet.

"We set up a crowdfunding campaign through the 'academist' site," continues Enoto, "in which we explained our scientific method and aims for the project. Thanks to everybody's support, we were able to make far more than our original funding goal."

Spurred by their success, the team built more detectors and installed them across the northwest coast of Honshu. And then in February 2017, four detectors installed in Kashiwazaki city, Niigata recorded a large gamma-ray spike immediately after a a few hundred meters away.

It was the moment the team realized they were seeing a new, hidden face of lightning.

When they analyzed the data, the scientists found three distinct gamma-ray bursts. The first was less than one millisecond in duration; the second was a gamma-ray afterglow that decayed over several dozens of milliseconds; and finally there was a prolonged emission lasting about one minute.

Enoto explains, "We could tell that the first burst was from the lightning strike. Through our analysis and calculations, we eventually determined the origins of the second and third emissions as well."

The second afterglow, for example, was caused by lightning reacting with nitrogen in the atmosphere. The gamma rays emitted in lightning have enough energy to knock a neutron out of atmospheric nitrogen, and it was the reabsorption of this neutron by particles in the atmosphere that produced the gamma-ray afterglow.

The final, prolonged emission was from the breakdown of now neutron-poor and unstable nitrogen atoms. These released positrons, which subsequently collided with electrons in annihilation events releasing gamma rays.

"We have this idea that antimatter is something that only exists in science fiction. Who knew that it could be passing right above our heads on a stormy day?" says Enoto.

"And we know all this thanks to our supporters who joined us through 'academist'. We are truly grateful to all."

The team still maintains over ten detectors on the coast of Japan, and are continually collecting data. They look forward to new discoveries that may await them, and Enoto hopes to continue seeing the participation of ordinary citizens in research, expanding the bounds of scientific discovery.

Explore further: Lightning produces afterglow of gamma radiation

More information: Teruaki Enoto et al, Photonuclear reactions triggered by lightning discharge, Nature (2017). DOI: 10.1038/nature24630

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33 comments

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cantdrive85
1.4 / 5 (10) Nov 22, 2017
Gamma rays and X-rays are created by electric discharge processes throughout the Universe, one of rhese days tge plasma ignoramuses will realize this fact. The gravity only guesses are outdated pre-spaceage fanciful beliefs.
Seeker2
3 / 5 (1) Nov 22, 2017
I was thinking you could smell the positrons after a lightening strike. Don't think I ever got that close though. Maybe it's a mixture of carbon and nitrogen isotopes.
Da Schneib
4 / 5 (4) Nov 22, 2017
Meh, the positrons weren't created by the lightning. They were released by a nuclear process that emits positrons, nitrogen decay. Do better physorg.

But the crowdsourcing is interesting.
JongDan
4.8 / 5 (4) Nov 22, 2017
I was thinking you could smell the positrons after a lightening strike. Don't think I ever got that close though. Maybe it's a mixture of carbon and nitrogen isotopes.

Probably just ozone, actually.
ursiny33
1 / 5 (4) Nov 22, 2017
positrons are i matter when they hit an electron it magnetically sticks to the electron , Scientists think it been annihilated because they can see it or measure it on any instruments they have , there is a reason for that a positron quantum charge mass is .33 percent smaller in charge mass than an electronit becomes a minority mass charge bound to the electron magnetically, and science can only measure the dominant mass charge or an equal mass charge the call neutral no charge, photons are made from 2 electrons and 3 positrons the 3 positrons have the same quantum charge mass as 2 electrons , when you break a photon apart they see 1 electron and a positron and a proton leaving to broken apart photon they classify the larger positively charged particle a proton because of it mass measured against the exiting positron but it really is just two positrons and the one electron that are still bound magnetically to each other not a proton in the break up of the photon
Whydening Gyre
5 / 5 (8) Nov 22, 2017
Gamma rays and X-rays are created by electric discharge processes throughout the Universe, one of
- (rhese days tge ) - plasma ignoramuses will realize this fact. The gravity only guesses are outdated pre-spaceage fanciful beliefs.

I see you've been samplin' the cooking sherry a little early, today...;-)
cantdrive85
1 / 5 (4) Nov 22, 2017
Gamma rays and X-rays are created by electric discharge processes throughout the Universe, one of
- (rhese days tge ) - plasma ignoramuses will realize this fact. The gravity only guesses are outdated pre-spaceage fanciful beliefs.

I see you've been samplin' the cooking sherry a little early, today...;-)

Galaxy S8 and fat fingers, what are you gonna do.....
Kron
5 / 5 (3) Nov 23, 2017
@Da Schneib,

So what was the cause of the beta decay in the atmospheric nitrogen?
Ojorf
2.7 / 5 (6) Nov 23, 2017
Yeah, I love the smell of positron in the morning.

Any idea why this can not be done in the lab? Why build detectors all over the place and wait for a fortuitous strike?
I'm sure there is a good reason. Just wondering.
antialias_physorg
5 / 5 (4) Nov 23, 2017
Meh, the positrons weren't created by the lightning. They were released by a nuclear process that emits positrons, nitrogen decay.

You can also get positron-electron generation with photons of sufficient energy (at least 1.02MeV - which is equivalent to the combined rest mass of a positron and an electron)

This is in the range of photons created during lightning strikes (ground lightning can deliver some photons as high as 2MeV.). I'm not sure why the nitrogen is pictured this way in the image above. An atom is needed because of conservation laws, but not a 'decay' the way it is shown.
dirk_bruere
5 / 5 (2) Nov 23, 2017
Who would have expected nuclear processes just from particles being accelerated by the millions of volts in a lightning strike?
Da Schneib
2.3 / 5 (3) Nov 23, 2017
@anti, I think that pair production would be a minority process, and in addition would result in gammas of the characteristic positron emission line, very promptly. The fact they don't seem to see such an emission line is why I think it's a minority process. It seems to me that pair production would have the effect of converting many photons to the positron emission line if it were common.

But I'm not sure enough of the sensitivity of the instruments to be certain of it.
gculpex
not rated yet Nov 23, 2017
So it is true, godzilla can control lightning!
antialias_physorg
5 / 5 (2) Nov 23, 2017
Well, they say they see 511MeV signals - which is a positron/electron annihilation (which you will get in either process).
I'm questioning whether the originating mechanism is (exclusively) the one they claim, because you can get positron/electron pairs created close to an atom without the atom actually being involved in a decay reaction.
The de-excitation cutoff they note is interesting, though and speaks of accelerated neutrons.

This paper finds 3 sources for lines
(1) deexcitation lines, (2) radiative neutron
capture lines, and (3) the positron annihilation line.

gaia.astro.umd.edu/~share/publications/murphy_11.pdf

which also posits another source:
The 0.511 MeV positron annihilation line is the
strongest line observed in the atmospheric spectrum and is
due to annihilation of positrons with ambient electrons. The
positrons result from the decay of pions produced in the
GCR shower and also from beta decay of radioactive nuclei
Da Schneib
5 / 5 (1) Nov 23, 2017
Thanks, @anti, I'll look it over.
Da Schneib
5 / 5 (2) Nov 23, 2017
Here's the version that was uploaded to arXiv in June, before revision and publication in Nature: https://arxiv.org...8044.pdf

I'll have a look at that too.
Da Schneib
5 / 5 (2) Nov 23, 2017
I will point out that the timing of the various signals is crucial to differentiate the signal from positrons created by pair creation from the prompt gammas directly generated by the lighting bolt itself as opposed to positrons released by the inverse beta decays, whereas the gammas from the neutron capture de-excitation will not show the strong 0.511 MeV line. So I'm going to be checking out the methods and data in these two papers quite carefully.
Whydening Gyre
5 / 5 (3) Nov 23, 2017
Gamma rays and X-rays are created by electric discharge processes throughout the Universe, one of
- (rhese days tge ) - plasma ignoramuses will realize this fact. The gravity only guesses are outdated pre-spaceage fanciful beliefs.

I see you've been samplin' the cooking sherry a little early, today...;-)

Galaxy S8 and fat fingers, what are you gonna do.....

Wasn't talking about the typos...:-)
Whydening Gyre
5 / 5 (3) Nov 23, 2017
So it is true, godzilla can control lightning!

No. That's Mothra...
Whydening Gyre
5 / 5 (2) Nov 23, 2017
Per the illustration at the top;
What I seem to be missing is, how does the unstable (13) nitrogen loses a PROTON to become 13Carbon...?
Isn't it just NEUTRON decay?
Da Schneib
5 / 5 (1) Nov 23, 2017
@Whyde, it's called inverse beta decay. A proton emits a positron and an electron neutrino and becomes a neutron. It's not a common decay path but if the energy levels are right then it's a possible one. Wikipedia has an article on it, or at least a mention and a quick search will turn it up.
Da Schneib
5 / 5 (1) Nov 23, 2017
@Anti, your quote does not refer to lightning. It refers to GCRs, which are galactic cosmic ray showers. In fact I don't think that paper has anything to do with lightning at all.

On page 4 of the arXiv version of the paper we are discussing here, the authors make the point:
What produced these positrons and how? A potential scenario is that electron-positron pairs are produced by high-energy gamma rays in the electron acceleration process. However, the lack of detection of high-energy seed gamma rays (>3 MeV, Fig. 3a, b) rejects the scenario. In addition, the environmental electric field measured on the ground was upwards during the annihilation signal (below ∼−3kV m), and hence positrons should not be accumulated towards the ground, and the annihilation line should not have been enhanced.

[contd]
Da Schneib
5 / 5 (1) Nov 23, 2017
[contd]
In addition to all this, as I argued above pair production positron emissions should be nearly as prompt as the gamma from the strike. This is because the gamma rays emerging from the strike will move at c, and positrons from that will not have a long mean free path before finding an atmospheric electron to annihilate with, emitting a 1.022 MeV gamma (the authors make the mistake of forgetting that the positron gamma is at this energy, and I did above too- realized it this time) which will again move at c. This would create an enhanced prompt 1.022 MeV signal which is not observed. By the time a microsecond has passed from the strike, the gammas are a thousand feet away, more or less. By the time a millisecond is over (which is the timescale they call "prompt") the gammas are two hundred miles from the strike site.
[contd]
Da Schneib
5 / 5 (1) Nov 23, 2017
[contd]
It does seem that their instrumentation is sensitive enough that it would not just show but differentiate any strong 1.022 MeV line during the first millisecond, then, if there were one. This would be good evidence of pair production. They apparently do not, instead seeing the 1.022 MeV line during the post-strike phase about 20-40 milliseconds downstream, by which point the gammas are thousands of miles away. They address this at the end of the paper, on pp 10-11 where they say:

[contd]
Da Schneib
5 / 5 (1) Nov 23, 2017
[contd]
An event associated with 0.511 MeV emission, similar to the event reported in this paper, was once detected previously at the same site on 13 January, 2012, after a pair of positive and negative discharges... since the electric-field monitor was not working at that time, we were unable to eliminate the pair production scenario entirely. ... In contrast, in the event reported in this paper, we measured the environmental electric-field... using a commercial electric field mill BOLTEK EFM-100, and found it to be negative during the delayed (annihilation) phase, which implies that electrons moved to the ground away from negatively charged clouds, and thus generating the 0.511 MeV line without emitting 10–20 MeV bremsstrahlung photons is impossible.
I'd say pair production is ruled out, and they were aware of the possibility and collected the data needed to do so.

I note that they also said 0.511 MeV again instead of 1.022 MeV.
Kron
1 / 5 (1) Nov 23, 2017
Since the positron and electron each have a mass of 511 keV the corresponding energy of the gamma photons produced upon their annihilation will also have the energy of 511 keV (given that 2 photons are produced as is most probable). Conservation of energy and linear momentum forbids the formation of only 1 photon in the event, so a 1022 keV photon will not emerge from the annihilation process (it is possible that more than 2 will be produced, though this is improbable except in some special cases).
Da Schneib
1 / 5 (1) Nov 23, 2017
Err, since the electron and positron each have 0.511 MeV of mass the gamma they produce by annihilation must have 1.022 = 0.511 x 2 MeV. The path for the momentum is obvious. It's trivial to produce a single summary vector from two vectors.

On Earth.

If you have enough quantum mechanics to show some actual scattering math to support your rank speculation about two gammas feel free to share it.

I ain't holdin my breath.
antialias_physorg
5 / 5 (1) Nov 24, 2017
Err, since the electron and positron each have 0.511 MeV of mass the gamma they produce by annihilation must have 1.022 = 0.511 x 2 MeV.

They produce two gammas with 511MeV each (since you need to have conservation of momentum).
Single photon annihilation (with one 1.022MeV photon) can only happen if you have a third party in the mix that can counteract the excess momentum of the released photon. (e.g. some charged particle that happens to be close by...this is in essence the reverse process by which a single 1.022MeV photon can create a positron/electron pair without actually hitting anything)

The nature of the two photon release is used in PET scanners. There you detect the two photons in opposing detectors and can, by the timing difference and the orientation of the detector, pinpoint the location where they originated. (They originate form an injected radioactive isotope that undergoes beta decay and the emitted positron almost immediately hits a close by electron)
Da Schneib
5 / 5 (1) Nov 24, 2017
Dang it, you're right @anti, my geometric intuition always betrays me on that one. Thanks man.
gculpex
not rated yet Nov 24, 2017
So it is true, Godzilla can control lightning!

No. That's Mothra...

Jokingly, Mothra has poison and hurricane winds with a strong right-wing uppercut.
watch the movie Space Godzilla for reference.

but as to the article, this seems to connect to space particles triggering lightning.
milnik
1 / 5 (3) Nov 24, 2017
First, we must distinguish lightning from the thunderbolt.
Lightning arises in the atmosphere in the collision of two opposite charges, where a higher electrical voltage is discharged at a lower voltage. With such a rapid movement of electrons through the air, an electron collision with air molecules occurs. External free electrons collide with an electronic coil of chemical elements in the atmosphere, where the electronic shell is removed from the nucleus and protons and neutrons remain. Now electrons are released from the neutron and new protons are formed, which with the existing protons have a higher positive charge of the nucleus than the electron around.
milnik
1 / 5 (3) Nov 24, 2017
First, we must distinguish lightning from the thunderbolt.
Lightning arises in the atmosphere in the collision of two opposite charges, where a higher electrical voltage is discharged at a lower voltage. With such a rapid movement of electrons through the air, an electron collision with air molecules occurs. External free electrons collide with an electronic coil of chemical elements in the atmosphere, where the electronic shell is removed from the nucleus and protons and neutrons remain. Now electrons are released from the neutron and new protons are formed, which with the existing protons have a higher positive charge of the nucleus than the electron around.
milnik
1 / 5 (3) Nov 24, 2017
Then there is an explosion of the nucleus from the proton and they are released from positrons, which enter into the reaction with the external electrons - the filaments, where the photons are formed, and the radiation and the gluon plasma is formed. At that passage of lightning, there is a vacuum and there the air enters, which causes the thunder-crash of air between one another. This is an event that scientists are eagerly waiting to say that it is an antimatter. There is no antimatter, there are only anti-charge particles.

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