Definition and basic physical description

Summary

Lightning is a natural weather phenomenon caused by electrostatic discharge between two electrically charged regions, which may both be within the atmosphere or one may be on the ground. After the discharge, the charged regions become partially or wholly electrically neutralized, and the event releases energy almost instantaneously, typically averaging between about 200 megajoules and 7 gigajoules. Physically, a lightning flash rapidly heats the surrounding air to extremely high temperatures (around 30,000 °C), producing a bright visible flash in some cases. It also emits electromagnetic radiation across a wide range of wavelengths, and it generates thunder: a sound produced by shock waves formed as the heated air near the discharge experiences a sudden pressure increase. Lightning most commonly occurs during thunderstorms, but it can also occur in other energetic weather systems such as volcanic eruptions.

Key Points

• 1

  Lightning is an electrostatic discharge between charged regions in the atmosphere (and sometimes between a cloud and the ground).

• 2

  A lightning flash releases energy nearly instantaneously, rapidly heats surrounding air, emits electromagnetic radiation, and produces thunder from shock waves.

• 3

  Lightning most commonly occurs in thunderstorms, but can also occur in other energetic events such as volcanic eruptions.