A small green flash of light that occasionally appears on the upper part of the sun as it rises or sets.

A brilliant coloration of the upper limb of the sun occasionally observed just as the sun’s apparent disk is about to sink below a distant clear horizon.

A momentary change in the color of the Sun, very occasionally observed in the last moments before the topmost reaches of the Sun dip below the western horizon, or in the first few moments after the Sun begins to rise on the eastern horizon. During the green flash, the strong reddish color caused by atmospheric reddening may, under certain circumstances, temporarily change to a vivid green. Usually, the flash, if seen at all, lasts for only a second or two, but when the observer is at a high latitude, so that the Sun is moving nearly parallel to the horizon, the "flash" may last for several minutes.