Lightning is a plasma and creates a powerful electromagnetic pulse across a wide range of frequencies as it releases the charge build up in a storm cloud. Thunderheads may be several thousand cubic kilometers in extent, yet all of their stored electrical energy travels down a discharge channel no wider than a man's waist. The z-pinch effect inside a lightning bolt's vortex causes rapid ionization, as well as particle acceleration fast enough to generate gamma rays.

-- MOTD jun 10 2010