Return stroke" redirects here. For other uses, see Return stroke (disambiguation). High-speed photography showing different parts of a lightning flash during the discharge process as seen in Toulouse, France. Maggio, Christopher R.; Marshall, Thomas C.; Stolzenburg, Maribeth (2009). "Estimations of charge transferred and energy released by lightning flashes in short bursts". Journal of Geophysical Research: Atmospheres. 114 (D14): D14203. Bibcode: 2009JGRD..11414203M. doi: 10.1029/2008JD011506.

Porter, Brett (1987). "Brett Porter, Photo in 1987, BBC:Ball lightning baffles scientists, day, 21 December, 2001, 00:26 GMT". Archived from the original on April 20, 2016.

The physical separation of charge into different regions using liquid water was demonstrated by Kelvin with the Kelvin water dropper. The most likely charge-carrying species were considered to be the aqueous hydrogen ion and the aqueous hydroxide ion. [18] Idone, V. P.; Orville, R. E.; Mach, D. M.; Rust, W. D. (1987). "The propagation speed of a positive lightning return stroke". Geophysical Research Letters. 14 (11): 1150. Bibcode: 1987GeoRL..14.1150I. doi: 10.1029/GL014i011p01150. Holton, James R.; Curry, Judith A.; Pyle, J. A. (2003). Encyclopedia of atmospheric sciences. Academic Press. ISBN 9780122270901. Archived from the original on November 4, 2017.

Petersen, Danyal; Bailey, Matthew; Beasley, William H.; Hallett, John (2008). "A brief review of the problem of lightning initiation and a hypothesis of initial lightning leader formation". Journal of Geophysical Research. 113 (D17): D17205. Bibcode: 2008JGRD..11317205P. doi: 10.1029/2007JD009036. Dry lightning is lightning that occurs with no precipitation at the surface and is the most common natural cause of wildfires. [93] Pyrocumulus clouds produce lightning for the same reason that it is produced by cumulonimbus clouds [ citation needed]. This term is mainly used in Australia, Canada, and the United States. Reprinted in: Vonnegut, B.; Vaughan, O. H. Jr.; Brook, M.; Krehbiel, P. (February 1985). "Mesoscale observations of lightning from Space Shuttle". Bulletin of the American Meteorological Society. 66 (1): 20–29. Bibcode: 1985BAMS...66...20Y. doi: 10.1175/1520-0477(1985)066<0020:MOOLFS>2.0.CO;2. hdl: 2060/19840024717. Lightning is usually produced by cumulonimbus clouds, which have bases that are typically 1–2km (0.62–1.24mi) above the ground and tops up to 15km (9.3mi) in height.

9. Volcanic lightning

A bolt from the blue (sometimes called ‘anvil lightning’ or ‘anvil-to-ground’ lightning) is a name given to a cloud-to-ground lightning discharge that strikes far away from its parent thunderstorm. It typically originates in the highest regions of a cumulonimbus cloud, travelling a good distance horizontally away from the thunderstorm before making a vertical descent to earth. Due to the final strike point being up to 10 miles away from the storm, these lightning events can occur at locations with clear ‘blue’ skies overhead - hence the name. Indeed, this is the origin of the term describing something unexpected: ‘out of the blue’!

Winter storms usually produce the greatest proportion of CG flashes in the UK. This is because lightning-producing clouds are associated with active cold and occluded fronts. Still, many are also embedded in the polar maritime air mass afterwards (the typical wintry showers which affect the country’s western half, producing soft hail) and marked on the synoptic charts as troughs. Given that the relatively warm sea is the source of instability, these showers can be present day and night and produce infrequent but very powerful CG flashes of up to ~300,000 amps! (typical lightning is ~20kA). Their bias towards powerful CG flashes is thought to be due to their sheared, low cloud tops. The positive charge at the top of these clouds overhangs the lower negative charge, which would otherwise screen the upper charge from the ground, encouraging a direct, powerful lightning flash between the top of the cloud and the ground. Rinnert, K. (1995). "9: Lighting Within Planetary Atmospheres". In Hans Volland (ed.). Handbook of Atmospheric Electrodynamics. CRC Press. p.204. ISBN 978-0-8493-8647-3. The requirements for the production of lightning within an atmosphere are the following: (1) a sufficient abundance of appropriate material for electrification, (2) the operation of a microscale electrification process to produce classes of particles with different signs of charge and (3) a mechanism to separate and to accumulate particles according to their charge.

The lightning bolt is a common insignia for military communications units throughout the world. A lightning bolt is also the NATO symbol for a signal asset.