New high speed camera techniques have revealed data that implies that lightning "branch" leaders are able to form in free air, away from the main branch - with which they later connect.
https://www.researchgate.net/p…itive_Leader_of_Lightning
Updated this post with a slow-mo GIF of leaders forming (slowed from a 10,000 fps video recording).
Related: Japanese team sees gamma ray pulse before lightning flash
And this is a 2015 paper on Positron annihilation detection: https://arxiv.org/abs/1505.03782
"We report the observation of two isolated clouds of positrons inside an active thunderstorm. These observations were made by the Airborne Detector for Energetic Lightning Emissions (ADELE), an array of six gamma-ray detectors, which flew on a Gulfstream V jet aircraft through the top of an active thunderstorm in August 2009. ADELE recorded two 511 keV gamma-ray count rate enhancements, 35 seconds apart, each lasting approximately 0.2 seconds. The enhancements, which were about a factor of 12 above background, were both accompanied by electrical activity as measured by a flat-plate antenna on the underside of the aircraft. The energy spectra were consistent with a source mostly composed of positron annihilation gamma rays, with a prominent 511 keV line clearly visible in the data. Model fits to the data suggest that the aircraft was briefly immersed in clouds of positrons, more than a kilometer across. It is not clear how the positron clouds were created within the thunderstorm, but it is possible they were caused by the presence of the aircraft in the electrified environment."
And this is a more journalistic account of the flight that led to the above paper:
Physicist finds mysterious anti-electron clouds inside thunderstorm
It is not clear how the positron clouds were created within the thunderstorm, b
Possible source 13-N, 15-O both are able to emit 511keV.
Possible source 13-N, 15-O both are able to emit 511keV.
That is only one of three possibilities already mentioned in the paper. And that particular route would also leave the question of how those nuclides could have been formed en masse.
The notion that stable "positron clouds" could exist within the atmosphere is also an interesting one in itself, regardless of how those particles were created. The sequence of detection indicated that particles were not being constantly anihilated in the air - as the characteristic 511keV photons were only being generated as the plane flew into the "zone" and disrupted some form of equilibrium.
I guess if a zone of air had a sufficient positive charge, then the positrons could possibly be "suspended" in the space between the air molecules without coming into contact with electrons that were tightly bound to the constituent atoms. But I've no idea (yet) at what charge level that would begin to be possible.
Another possible suggestion, in the paper, is that the positrons were somehow being created by the action of the plane through the air, in that particular zone - which, of course, would be equally mysterious.
511keV
This signal can only occur inside mass. Free e +/- annihilation is a 3 photon process that very rarely gives a 511keV photon.
See::
D.Kaminska at all, A feasibility study of ortho-positronium decays measurement with the J-PET scanner based on plastic scintillators, DOI 10.1140/epjc/s10052-016-4294-3 , 2016
how those nuclides could have been formed en masse
2017 enomoto et al
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2020JD033194
The atmospheric photonuclear reactions 14N (γ, n) 13N and 16O (γ, n) 15O generate fast neutrons
with a kinetic energy of E0 ∼ 10 MeV and unstable radioactive isotopes, which generate positrons
in beta-plus decays
It should be interesting to know the current (A) threshold for that , to compare with discharges experiments we know.
Now maybe the climate change is coming from this phenomenon, thunderstorms should be banned 
Display More2017 enomoto et al
https://arxiv.org/abs/1711.08044
https://agupubs.onlinelibrary.…full/10.1029/2020JD033194
https://www.nature.com/articles/nature24630
The atmospheric photonuclear reactions 14N (γ, n) 13N and 16O (γ, n) 15O generate fast neutrons
with a kinetic energy of E0 ∼ 10 MeV and unstable radioactive isotopes, which generate positrons
in beta-plus decays
At those gamma energies you could get direct electron-positron pair production without needing any unstable positron emitting nuclides.
The notion that stable "positron clouds" could exist within the atmosphere is also an interesting one in itself, regardless of how those particles were created. The sequence of detection indicated that particles were not being constantly anihilated in the air - as the characteristic 511keV photons were only being generated as the plane flew into the "zone" and disrupted some form of equilibrium.
Since the tops of thunderclouds are normally positively charged, and the bottom negatively charged, with a PD of possibly a few million volts, the interior may contain zones of charged plasma. This is a Safire reactor in the sky.
Since the tops of thunderclouds are normally positively charged, and the bottom negatively charged, with a PD of possibly a few million volts, the interior may contain zones of charged plasma.
Which would be the natural assumption - except, the Dwyer & Uman paper reckons there isn't enough PD, over a short enough distance, for a spark.
Display More2017 enomoto et al
https://arxiv.org/abs/1711.08044
https://agupubs.onlinelibrary.…full/10.1029/2020JD033194
https://www.nature.com/articles/nature24630
The atmospheric photonuclear reactions 14N (γ, n) 13N and 16O (γ, n) 15O generate fast neutrons
with a kinetic energy of E0 ∼ 10 MeV and unstable radioactive isotopes, which generate positrons
in beta-plus decays
These papers all make assumptions that seem slightly dubious, to me. The claim that the gamma flashes are bremsstrahlung seems to ignore that the pulses only seem to be generated during the leader phase, and stop before the main strike commences. And, as far as I know, neutrons have not been definitely recorded yet (although people are actively searching for them).
Also, although the positron annihilation gammas are detected for some time after the strike, that does not prove that the positrons are necessarily being created at that time (as is asserted in one paper). If they were created earlier (during the leader gamma flashes) - and were being "stored" in a highly positively charged cloud zone - then the sudden reduction in zone charge, due to the main lightning discharge, could subsequently allow the existing positrons to commence annihilation.
...there isn't enough PD, over a short enough distance, for a spark.
I agree, but the distance between the base and the top of a thundercloud can be as much as 20 kilometers. even a small voltage gradient mounts up over that distance.
I just wanted to add that Santilli was one of the first researchers I knew about proposing that lightnings were causing nuclear reactions and he also insisted the current content of N in the atmosphere could only be explained that way.
Regarding Alan Smith ’s “SAFIRE reactor in the sky” idea, the people of the “Electric Universe” propose that the whole atmosphere and water in it are a plasma system that is much more under the influence of electrostatic forces than anyone would like to reckon. There are a few talks given by Gerald Pollack within Electric Universe conferences, one of those deals exclusively with the electrostatic forces that he proposes keep clouds in the sky and how rain may be primarily electrostatically driven. This talk may sound as total nonsense to anyone that thinks the major forces in the atmosphere are merely gravitational and thermal convection, but watching the talk and hearing the proposed mechanisms is tantalizing. As Alan Smith mentions, The electrostatic potential in the atmosphere builds a lot with distance.
Here’s Pollack’s talk on the topic, charge separation smack in the title:
I just wanted to add that Santilli was one of the first researchers I knew about proposing that lightnings were causing nuclear reactions and he also insisted the current content of N in the atmosphere could only be explained that way.
Conversely, of course, (low energy) nuclear reactions could be causing lightning... 
(Or, at the very least, triggering it.)
I agree, but the distance between the base and the top of a thundercloud can be as much as 20 kilometers. even a small voltage gradient mounts up over that distance.
Agreed - but to get the two opposite high voltage regions to conductively connect, so a discharge can take place, something probably has to open up an ionised channel. The "stepped leaders" seem to achieve that - but as the video clip further up this thread shows, the leaders seems to fly around in a pattern reminiscent of some airburst fireworks (but at many times the speed). The tips almost appear to be self-propelled - and semi-random in their direction (although there is some fanning-out). In other words, they don't seem to be largely driven by charge gradient.
It seems that the appearance of these leaders is coincident with the gamma ray bursts - but whether this is a cause & effect situation, and, if so, which might causes which, we still don't know.
And then it will only get worse....
This talk may sound as total nonsense to anyone that thinks the major forces in the atmosphere are merely gravitational and thermal convection, but watching the talk and hearing the proposed mechanisms is tantalizing
