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Lightning Can Cause Nuclear Reactions and Generate Antimatter

posted by Fnord666 on Thursday November 23 2017, @09:48AM   
from the so-that's-what's-in-the-warp-nacelles dept.

takyon writes:

Lightning can transmute nitrogen into carbon-14 and cause the emission of a positron, the antimatter counterpart of the electron:

Lightning can accelerate some electrons to almost the speed of light, and the electrons can then produce γ-rays. [Leonid] Babich proposed that when one of these γ-rays hits the nucleus of a nitrogen atom in the atmosphere, the collision can dislodge a neutron. After briefly bouncing around, most of the neutrons get absorbed by another nitrogen nucleus. This adds energy to the receiving nucleus and puts it in an excited state. As the receiving nucleus relaxes to its original state, it emits another γ-ray — contributing to the giveaway γ-ray glow.

Meanwhile, the nitrogen nucleus that has lost one neutron is extremely unstable. It decays radioactively over the next minute or so; in so doing, it emits a positron, which almost immediately annihilates with an electron, producing two 511-keV photons. This was the third signal, Enoto says. He suspects that his detectors were able to see it only because the briefly radioactive cloud was low, and moving towards the detectors. This combination of circumstances might help to explain why the photonuclear signature has been seen so rarely. Enoto says that his team has observed a few similar events, but that the one described in the paper is the only clear-cut event so far.

Babich also predicted that not all of the neutrons dislodged from nitrogen by a γ-ray are absorbed. Some of them instead will trigger the transmutation of another nitrogen nucleus into carbon-14, a radioactive isotope that has two more neutrons than ordinary carbon. This isotope can be absorbed by organisms; it then decays at a predictable rate long after the organism's death, which makes it a useful clock for archaeologists.

The main source of the carbon-14 in the atmosphere has generally been considered to be cosmic rays. In principle, lightning could also contribute to the supply. But it is not clear yet how much of the isotope is produced in this way, says Enoto, in part because it's possible that not all bolts initiate photonuclear reactions.

Photonuclear reactions triggered by lightning discharge (DOI: 10.1038/nature24630) (DX)

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Original Submission

• Re:News? (Score: 5, Informative) by Yog-Yogguth on Thursday November 23 2017, @03:01PM

  by Yog-Yogguth (1862) on Thursday November 23 2017, @03:01PM (#600674) Journal

  The difference seems to be "definitive proof" (rather than "not observed conclusively" but everybody accepting it as the only explanation), at least according to the abstract of the paper. I'll paste it here and add some splashes of bold, the stuff before the first bold sentences sort of sums up the past and the stuff after that is what they did and the last bold sentence is the claim being made:

  Lightning and thunderclouds are natural particle accelerators1. Avalanches of relativistic runaway electrons, which develop in electric fields within thunderclouds2,3, emit bremsstrahlung γ-rays. These γ-rays have been detected by ground-based observatories4,5,6,7,8,9, by airborne detectors10 and as terrestrial γ-ray flashes from space10,11,12,13,14. The energy of the γ-rays is sufficiently high that they can trigger atmospheric photonuclear reactions10,15,16,17,18,19 that produce neutrons and eventually positrons via β+ decay of the unstable radioactive isotopes, most notably 13N, which is generated via 14N + γ → 13N + n, where γ denotes a photon and n a neutron. However, this reaction has hitherto not been observed conclusively, despite increasing observational evidence of neutrons7,20,21 and positrons10,22 that are presumably derived from such reactions. Here we report ground-based observations of neutron and positron signals after lightning. During a thunderstorm on 6 February 2017 in Japan, a γ-ray flash with a duration of less than one millisecond was detected at our monitoring sites 0.5–1.7 kilometres away from the lightning. The subsequent γ-ray afterglow subsided quickly, with an exponential decay constant of 40–60 milliseconds, and was followed by prolonged line emission at about 0.511 megaelectronvolts, which lasted for a minute. The observed decay timescale and spectral cutoff at about 10 megaelectronvolts of the γ-ray afterglow are well explained by de-excitation γ-rays from nuclei excited by neutron capture. The centre energy of the prolonged line emission corresponds to electron–positron annihilation, providing conclusive evidence of positrons being produced after the lightning.

  I could be wrong, I'm not a physicist.

  --
  Bite harder Ouroboros, bite! tails.boum.org/ linux USB CD secure desktop IRC *crypt tor (not endorsements (XKeyScore))

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