This is the third post on atmospheric optical phenomena we’ve seen in Antarctica. The previous post detailed sun halos. This post will cover sun dogs (parhelia) and sun pillars.

Above: Sun dogs (parhelia) and a sun pillar over NSF Discovery Pier and Hut Ridge, viewed from town.

Sun dogs, also known as parhelia, appear directly to the right and left of the sun. In the photo above one can be seen to the left of the sun, directly above Discovery Pier. Sun pillars are seen as a pillar of light from the top of the sun shooting skyward. The sun pillar in the above photo is a smaller example, but clearly visible. Both of these effects form under similar conditions as sun halos – namely the presence of suspended ice crystals in the atmosphere. Sun dogs are formed by the refraction of light through ice crystals and sun pillars are formed by the reflection of light off the faces of ice crystals. The sun halos in the last optical phenomena post were formed by ice crystals in high altitude cirrus clouds. This is the most common way to get these effects but not the only way. The ice crystals that produce the effects pictured above are formed by fog droplets that have frozen due to extremely low temperatures (this type of fog is nicknamed “diamond dust”). Even though many atmospheric optical effects are caused by refraction through and reflection from ice crystals, the exact phenomenon depends on the crystals’ shape, orientation, and the surrounding conditions. That’s why the crystals in the previous post produced only sun halos, while the ones in this post created sun dogs and a small sun pillar, with only an extremely faint halo present. There are other effects formed by these ice crystals, such as the upper tangent arc (a small arc facing upwards at the zenith of the halo), which I hope to see someday!

Above: A zoomed in photo of the parhelion to show the shape and slight rainbow light.