The only kind of dogs we have at South Pole
Without looking it up, why do you think that Sun Dogs appear on the left and right of the sun? There is sometimes a halo, and to me radial symmetry seems natural; so what’s special about the right and left that would account for parhelia?
Feel free to discuss in comments, but one rule: No looking up. And if you really really know, feel free to sit back and watch the guessing.
barryontheice 
my guess: there’s less atmosphere on the top. The bottom’s all filled up with clouds and horizon.
.. but the dogs are often there when there’s also a full halo.
Ahhh, Light & Color In The Outdoors, how I love you. http://www.amazon.com/Light-Color-Outdoors/dp/0387979352/
Flaky shaped ice crystals with a strong preference for orientation?
It’s gonna take polarization to create an explanation out of that.
I think the “left and right” can actually be connected in a arc that goes around the whole “dome” of the sky, and the dogs are at the intersection of that arc and the 22degree circle arc. Gradient of atmosphere thickness relative to the observer per yduJ above, makes sense, but sundogs occur at many elevations in the sky so the thickness changes.
So i dunno, but i’m off to the http://www.atoptics.co.uk/index.htm site to refresh my memory.