Lightning Produces Gamma Rays

Weird huh? I read this as an aside in a book and chased it down this morning. My first thought was that this was either a) some kind of synchotron radiation produced by a variation of the Tademaru Effect or b) pair production (!)!

Their report suggested that runaway breakdown at a much lower altitude, created within "strong fields in or just above the thundercloud," could have triggered the TGFs instead. "It still almost certainly has to be runaway breakdown that's creating these," Cummer said. "The only real possibility is that it's much closer to the cloud top, and linked to something else happening inside the cloud." The detailed Duke-led analysis also disclosed that, on average, TGFs occurred 1.24 milliseconds before their associated lightning strokes. "That was something we absolutely were not expecting," Cummer said. "But the coincidence between the lightning and the TGFs we found is too good to be random. So, even if the TGFs precede the lightning, they are in some way connected." Their paper suggests one possibility for such a negative cause-and-effect relationship. Perhaps "TGFs are produced by a process associated with the development of the observed lightning stroke, but that actually occurs about 1 millisecond before the stroke itself," the authors wrote.

I'm wondering if there is a spectrum of low-frequency microwaves near (but not necessarily colocated with )the source before the gamma burst. The Tademaru Effect could explain it, i.e. the microwaves could produce a few relativistic electrons which then crash and dump their energy in the form of gamma. There would be a characteristic gamma spectrum if this were true, so it's testable.