Types
The "green flash" description relates to a group of optical phenomena, some of which are listed below:
| Type | Characteristics | Conditions | Best seen from... |
|---|---|---|---|
| Inferior-mirage flash | Joule's "last glimpse"; oval, flattened below; lasts 1 or 2 seconds | Surface warmer than the overlying air | Close to sea level |
| Mock-mirage flash | Indentations seem to "pinch off" a thin, pointy strip from the upper rim of the Sun; lasts 1 or 2 seconds | Atmospheric inversion layer below eye level; surface colder than air | The higher the eye, the more likely; flash is most obvious when the eye is just above the inversion. |
| Sub-duct flash | Large upper part of an hourglass-shaped Sun turns green for up to 15 seconds; | Observer below a strong atmospheric inversion | In a narrow height interval just below a duct (can occur at any height) |
| Green ray | Green beam of light either shooting up or seen immediately after sundown; usually few degrees long, lasting several seconds | Hazy air and a bright green flash acting as a light source | Sea level |
The majority of flashes observed are inferior-mirage or mock-mirage effects, with the others constituting only 1% of reports. Some types not listed in the table above, such as the cloud-top flash (seen as the sun sinks into a coastal fog, or at distant cumulus clouds), are not understood.
Read more about this topic: Green Flash
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