Lightning

What is Lightning?

Lightning is an electrical discharge in the atmosphere, very similar to a spark. It is the electrical breakdown of insulating air to provide a transient, conductive path along which a current can run to neutralize the charge.

Where and why does lightning occur?

Lightning mostly occurs in thunderstorms. Other situations in which lightning occurs are dust storms, blizzards, volcanic eruptions and nuclear explosions. It seems to be a phenomenon occurring in large volumes of particle clouds when they are being transported in the atmosphere.
Simplified, a thunderstorm has a positively charged top, a negatively charged lower section, and a small layer of positive charge at the cloud base which is carried up a little bit into the updrafts. We call the top (+) charged region the P region, the lower (-) charged region the N region, and the (+) charge nears the base, the p region.