What is the GREEN flash?

A green flash, or ray, is a natural phenomenon that is commonly seen at sunset, but also occurs during sunrise. As the sun rises or lowers over the horizon, a rare green flash will appear given the right atmospheric conditions. The green ray only appears for a few seconds, hence the usage of the term flash.

The optimum conditions for observing a green flash are: clear air and an unobstructed horizon. The clearer the air the better as pollutants or dust particles in the air will prevent certain light wavelengths from passing. A lower apparent horizon is necessary because the light from the setting sun will refract through the atmosphere.  Green flashes are seen more on the ocean because of the extra amount of atmosphere the observer is looking through at the horizon as the sun is rising or setting. Observing from mountain heights works just as well, too.


Image taken from: http://www.coastalwebweaver.com/greenflash.html#aty

Several effects take place. A mirage will often have to occur to distort the image of the sun. When the sun sets light waves are refracted through the atmosphere. Blue light is scattered more than the red or green light because it has a closer resonance to the atmosphere (Hicks, 2006).
The image below will help to better understand.


Image taken from: http://www.coastalwebweaver.com/greenflash.html#aty

Home            Not only Green!            History            Additional Resources            References