Lightnings

Lightning is a rapid electrical discharge that occurs during thunderstorms and, less commonly, in other atmospheric discharges. It results from the separation of electrical charges within cumulonimbus clouds, creating a substantial potential difference between regions of the cloud or between the cloud and the ground. When the electrical field becomes strong enough, a conductive channel forms, and a discharge rapidly equalizes the charge. The visible flash is produced by the sudden heating and ionization of air along the channel, reaching temperatures around 30,000 kelvin; the accompanying thunder is the sound of rapidly expanding air.

There are several types of lightning: cloud-to-ground, where a discharge travels from cloud to Earth; intra-cloud, within a single cloud; and cloud-to-cloud, between separated clouds. A typical cloud-to-ground discharge begins with a stepped leader that propagates from the cloud in short jumps, followed by a return stroke along the same path, producing the bright flash. A single thunderstorm can generate multiple strokes in quick succession.

Electrical characteristics vary widely. Peak currents commonly range from about 5 to 30 kiloamperes, but can be higher or include multiple strokes. The global incidence is very high; estimates suggest roughly 1.4 billion flashes occur worldwide each year.

Lightning can pose serious hazards to people, buildings, and aviation, and can ignite wildfires. Safety guidelines emphasize seeking shelter indoors, avoiding water, and staying away from conductive objects during a storm. Lightning also plays a role in the Earth’s electrical system, helping balance charge between the atmosphere and the surface and contributing to atmospheric chemistry through the production of nitrogen oxides.