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Halos, Sundogs, and Sun Pillars
• The sub duct mirage is interesting, because it shows the sun's image as an hourglass shape. The upper part of the hourglass will be green.
• A Green Ray is very unusual and is a Green flash of light or beam of light you see shooting up from a Green flash. This is so rare that has not been photographed.
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Figure 44 is a nice image of the sun setting and a Green flash.
Figure 44
If you want to see one yourself, the sky must be clear and you need an unobstructed view of the sunrise or sunset. These conditions usually mean the Green flash is best seen over water, although you may see it from an airplane, a mountaintop, or a very tall building, because you can see the distant horizon of these locations.
HALOS, SUNDOGS, AND SUN PILLARS
There are several other interesting Sun -related phenomena you might see. Many of these are seen only on very cold days when there are lots of ice crystals in the sky. They
are caused by the refraction of light off of these ice crystals. Exactly what you see will depend on how far up into the atmosphere these ice crystals reach. It might also depend on the size and shape of these ice crystals. The term refraction means the bending of light. We will talk more about that later.
Most ice crystals are hexagonal shape, just like snowflakes only perhaps more boring. When we see them in cold weather near the ground, we call them diamond dust. You need to know, however, that ice crystals are not always the same shape. Some can be more columnar in shape, while others are platelike. When we talk about refraction with ice crystals, there only 2 angles of refraction or bending to consider. These are 60 degrees or 90 degrees. The phenomenon you see depends on what angle light is being refracted.
Halos, on the other hand, can be 22 degree or 46 degree halos. These are called by different degree names based on the angle light is being refracted off of ice crystals. You may see them anytime of the year; however, the wintertime is best because of the cold weather and better conditions existing then for ice crystals to be present in the atmosphere.
Figure 45.
