Lightning and Neutrons

http://arstechnica.com/science/news/2012/03/nuclear-lightening.ars

-: inexplicata of the day :-

Lightning strikes produce free neutrons, and we're not sure how

Scientists confirm that lightning strikes generate low energy neutrons, but eliminate both of the explanations we had for how this might work.
http://dx.doi.org/10.1103/PhysRevLett.108.125001