http://physics.aps.org/synopsis-for/10.1103/PhysRevLett.110.185005
"After centuries of observation, lightning is still a puzzle: it is not yet fully known how thunderclouds acquire electrical charge and what initiates the discharge. Two factors are thought to be important: small water or ice particles inside clouds (so-called hydrometeors) and showers of electrons created by cosmic rays. In Physical Review Letters, Alex Gurevich at the Russian Academy of Science, and Anatoly Karashtin at the Radiophysical Research Institute, Nizhny Novgorod, Russia, report a new analysis of radio pulses emitted at the onset of lightning strikes, suggesting how lightning initiation can arise from a combination of the two factors. Specifically, they show microdischarges at hydrometeors can amplify cosmic-ray-initiated breakdown." <more>
