I’m back home for a day or two from the north. Lots of interesting things but as I’m catching up on sleep before returning for another stint, I’ll just post one note. I was surveying all the riparian zones on our project (I get most of the work on foot as I’m the only one who enjoys it) when I traversed along this unnamed frozen lake. I did a bit of a double take when I realized there was a gorgeous rainbow halo on the ground in the snow!
It then occurred to me I have never seen a halo on the ground before. I took this picture with my iphone but of course the halo merely looks like a lens effect. It’s only an interesting picture if you understand that the halo exists in the world and not just the camera. Upon getting home yesterday, I looked up the phenomenon to discover it is very uncommon and could only find a handful of pictures of it. This is the more common 22 degree ground halo. There is an even rarer 42 degree halo as well. 
Above: 22 degree ground halo taken 11am, Jan 18, 2015 @ lat. 55N
To create this halo, ice crystals need to form and settle in a very precise way. As I’m always saying, there’s always something new and astounding in the bush if you spend enough time out in it.
daviditron 
With stable weather, ought you to be able to find it on successive days (for a given sun angle)?
Not sure. The problem is you can only see it when sun is out meaning there will necessarily be a big temperature swing in next 12 hours when the sun sets. This will result in crystal alteration and deposition as moisture in the warmed air crystallizes as the temperature drops. The fact I’ve never seen this before in all my days in the wilds leads me to wonder just how long the right conditions can persist?