lightning

Lightning is a rapid electrostatic discharge in the atmosphere, resulting from the separation of electric charges within a thundercloud or between a cloud and the ground. As a cumulonimbus cloud develops, collisions between ice and water particles transfer charges, causing the cloud's lower region to become negatively charged and the upper region to become positively charged. When the electric potential between regions becomes large enough, air breaks down and a conductive plasma channel forms, producing a bright flash.

Typically a lightning event begins with a stepped leader propagating in the air toward the ground or another cloud. When it nears a region of opposite charge, a return stroke travels along the channel, producing the visible flash. Some events involve multiple strokes and continuing currents. Common types include cloud-to-ground, intra-cloud, and cloud-to-cloud discharges; ground-to-cloud flashes are rare.

Lightning channels heat the surrounding air to temperatures around 30,000 kelvin, causing rapid expansion and the thunder that often accompanies the flash. The discharge lasts microseconds to milliseconds, and currents in a single stroke commonly range from a few to several tens of kiloamperes, with peak currents occasionally exceeding 100 kA.

Global lightning activity averages around tens of flashes per second, with most occurring in tropical and subtropical regions during warm seasons. It is a major cause of wildfires and can damage electrical systems, aviation, and regional infrastructure.

Scientists study lightning with ground-based networks, weather radars, optical sensors, and radio measurements to locate, map, and characterize strokes. Safety measures include proper grounding of buildings, lightning rods, surge protection, and avoiding tall structures during storms.