Crown flash is a rarely observed

meteorological phenomenon This glossary of meteorology is a list of terms and concepts relevant to meteorology and atmospheric science, their sub-disciplines, and related fields. A ...

involving "The brightening of a thunderhead crown followed by the appearance of aurora-like streamers emanating into the clear atmosphere". The current

hypothesis A hypothesis (plural hypotheses) is a proposed explanation for a phenomenon. For a hypothesis to be a scientific hypothesis, the scientific method requires that one can test it. Scientists generally base scientific hypotheses on previous obse ...

for why the phenomenon occurs is that

sunlight Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is scattered and filtered through Earth's atmosphere, and is obvious as daylight when t ...

is reflecting off, or refracting through, tiny

ice crystals Ice crystals are solid ice exhibiting atomic ordering on various length scales and include hexagonal columns, hexagonal plates, dendritic crystals, and diamond dust. Formation The hugely symmetric shapes are due to depositional growth, n ...

above the crown of a

cumulonimbus cloud Cumulonimbus (from Latin ''cumulus'', "heaped" and ''nimbus'', "rainstorm") is a dense, towering vertical cloud, typically forming from water vapor condensing in the lower troposphere that builds upward carried by powerful buoyant air currents. ...

. These ice crystals are aligned by the strong

electric field An electric field (sometimes E-field) is the physical field that surrounds electrically charged particles and exerts force on all other charged particles in the field, either attracting or repelling them. It also refers to the physical field fo ...

effects around the cloud, so the effect may appear as a tall (sometimes curved) streamer, pillar of light, or resemble a massive flash of a

searchlight A searchlight (or spotlight) is an apparatus that combines an extremely bright source (traditionally a carbon arc lamp) with a mirrored parabolic reflector to project a powerful beam of light of approximately parallel rays in a particular direc ...

flashlight A flashlight ( US, Canada) or torch ( UK, Australia) is a portable hand-held electric lamp. Formerly, the light source typically was a miniature incandescent light bulb, but these have been displaced by light-emitting diodes (LEDs) since the ...

beam. When the electric field is disturbed by electrical

charging Charging may refer to: * Charging (ice hockey), when a player takes more than three steps before checking an opposing player * Battery charger, a device used to put energy into a rechargeable battery * Charging station, a device used for recharging ...

or discharging (typically, from

lightning Lightning is a naturally occurring electrostatic discharge during which two electric charge, electrically charged regions, both in the atmosphere or with one on the land, ground, temporarily neutralize themselves, causing the instantaneous ...

) within the cloud, the ice crystals are re-oriented causing the light pattern to shift in a characteristic manner, at times very rapidly and appearing to 'dance' in a strikingly mechanical fashion. The effect may also sometimes be known as a "leaping sundog". As with sundogs, observation of the effect is dependent upon the observer's position - it is not a self-generated light such as seen in a lightning strike or

aurora An aurora (plural: auroras or aurorae), also commonly known as the polar lights, is a natural light display in Earth's sky, predominantly seen in high-latitude regions (around the Arctic and Antarctic). Auroras display dynamic patterns of bri ...

, but rather a changing reflection or refraction of the sunlight. Unlike

sundogs A sun dog (or sundog) or mock sun, also called a parhelion (plural parhelia) in meteorology, is an atmospheric optical phenomenon that consists of a bright spot to one or both sides of the Sun. Two sun dogs often flank the Sun within a 22° ...

however (which are also caused by refraction of sunlight through ice crystals), the crown flash effect appears localised directly above the cloud. The first scientific description of the crown flash phenomenon appears to be in the journal

Monthly Weather Review The ''Monthly Weather Review'' is a peer-reviewed scientific journal published by the American Meteorological Society. It covers research related to analysis and prediction of observed and modeled circulations of the atmosphere, including technique ...

in 1885, according to the

Guinness Book of Records ''Guinness World Records'', known from its inception in 1955 until 1999 as ''The Guinness Book of Records'' and in previous United States editions as ''The Guinness Book of World Records'', is a reference book published annually, listing world ...

. Also mentioned in ''

Nature Nature, in the broadest sense, is the physics, physical world or universe. "Nature" can refer to the phenomenon, phenomena of the physical world, and also to life in general. The study of nature is a large, if not the only, part of science. ...

'' in 1971 and in a letter to ''Nature'' slightly earlier in the same year, this

phenomenon A phenomenon ( : phenomena) is an observable event. The term came into its modern philosophical usage through Immanuel Kant, who contrasted it with the noumenon, which ''cannot'' be directly observed. Kant was heavily influenced by Gottfried W ...

is regarded as uncommon and not well documented. Starting with an initial video upload in 2009 dozens of

YouTube YouTube is a global online video platform, online video sharing and social media, social media platform headquartered in San Bruno, California. It was launched on February 14, 2005, by Steve Chen, Chad Hurley, and Jawed Karim. It is owned by ...

videos have since been emerging that appear to document this phenomenon.

References

{{reflist

External links

* "Leaping Streams of Light: A new natural phenonmenon?" - 2011 - http://forgetomori.com/2011/science/leaping-streams-of-light-a-new-natural-phenomenon/ * Discover Magazine - 2011 - http://blogs.discovermagazine.com/badastronomy/2011/10/25/amazing-video-of-a-bizarre-twisting-dancing-cloud/ Lightning Atmospheric optical phenomena

See also

References

External links