| 词条 | Crown flash |
| 释义 |
Crown flash is a rarely observed weather phenomenon involving "The brightening of a thunderhead crown followed by the appearance of aurora-like streamers emanating into the clear atmosphere".[1] The current hypothesis for why the phenomenon occurs is that sunlight is reflecting off or refracting through tiny ice crystals above the crown of a cumulonimbus cloud. These ice crystals are aligned by the strong electro-magnetic effects around the cloud,[2] so the effect may appear as a tall streamer, pillar of light, or resemble a massive flash of a searchlight / flashlight beam. When the electro-magnetic field is disturbed by electrical charging or discharges (lightning flashes) within the cloud, the ice crystals are re-orientated causing the light pattern to shift, at times very rapidly and appearing to 'dance' in a strikingly mechanical fashion.[3] The effect may also sometimes be known as a "leaping sundog". As with sundogs, the observer would have to be in a specific position to see the effect, which is not a self-generated light such as seen in a lightning strike or aurora, but rather a changing reflection/refraction of the sunlight. Mentioned in Nature in 1971[4] and in a letter to Nature slightly earlier in the same year,[5] this phenomenon is regarded as rare and not well documented. Starting in 2009 several YouTube videos have since emerged that appear to document this phenomenon.[6] See also
References1. ^{{cite book|last1=Corliss|first1=William|title=Lightning, Auroras, Nocturnal Lights, and Related Luminous Phenomena: A Catalog of Geophysical Anomalies|date=1982|isbn=978-0915554096}} 2. ^{{cite journal|last1=Vonnegut|first1=B|title=Orientation of Ice Crystals in the electric field of a Thunderstorm|journal=Weather|date=1965|volume=20|issue=10|pages=310–312|url=http://amasci.com/amateur/vonngt_1965.txt|doi=10.1002/j.1477-8696.1965.tb02740.x|bibcode = 1965Wthr...20..310V }} 3. ^{{cite web|url=http://forgetomori.com/2011/science/a-new-natural-phenomenon-crown-flash/|accessdate=2015-09-03|title=A New Natural Phenomenon - Crown Flash}} 4. ^{{cite journal|last1=Graves|first1=Maurice E.|last2=Gall|first2=John C.|last3=Vonnegut|first3=Bernard|title=Meteorological Phenomenon called Crown Flash|journal=Nature|date=1971|volume=231|issue=5300|page=258|doi=10.1038/231258a0|bibcode = 1971Natur.231Q.258G|pmid=16062656}} 5. ^{{cite journal|last1=Graves|first1=Maurice E|last2=Gall|first2=John C|title=Possible Newly Recognized Meteorological Phenomenon called Crown Flash|journal=Nature|date=1971|volume=229|pages=184–185|doi=10.1038/229184b0|bibcode = 1971Natur.229..184G|pmid=16059137}} 6. ^{{cite web|title=YouTube Playlist of Crown Flashes by upload date|url=https://www.youtube.com/playlist?list=PLwpZXX1s8mYFAqSwULeotcPI-84JKW9jk|accessdate=2018-08-28}} External links
2 : Lightning|Atmospheric optical phenomena |
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