A sun dog is an uncommon type of halo, or an atmospheric optical phenomenon associated with the sun. The scientific name for the phenomenon is parhelion (Plural parhelia). It occurs due to internal reflection in ice crystals which accounts for its relative rarity - it is only produced in clouds cold enough to be ice rather than water, which only occurs far below 0°C. These clouds are usually thin and high up. Sundogs (and other associated phenomena such as sun pillars) are common in Antarctica. They occur horizontally either side of the sun at an angular separation of 22 degrees.

In remote streches of Western Texas, sundog refers colloquially to a segment of a common rainbow.

External links

• http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/opt/ice/sd.rxml
• http://www.astrophys-assist.com/wilobs/weathwin/sundog.htm
• http://www.sundog.clara.co.uk/atoptics/phenom.htm

Sun dog could also refer to:

• The Sun Dog is a short story by Stephen King.
• SunDog: Frozen Legacy is a computer game originally developed in 1984 for the Apple II.
• Iridescent cloud