It's been a great day for seeing a halo around the Sun. It started with this upper arc that was showing the full spectrum. Later there was a full halo with the requisite two sun dogs to the right and left of the Sun.
Today I noticed for the first time that the sun dogs weren't quite on the halo itself: they are just beyond. All of these phenomena come from the refraction of light through ice crystals very high in the atmosphere. Start here:
https://en.wikipedia.org/wiki/Halo_(optical_phenomenon) and here
https://en.wikipedia.org/wiki/Sun_dog This halo is 22 degrees from the Sun
https://en.wikipedia.org/wiki/22%C2%B0_halo
I was even more excited by two phenomena I hadn't seen before.
The first was a small section of an outer 46 degree halo. It is just by the right hand side of the washing line.
https://en.wikipedia.org/wiki/46%C2%B0_halo The second is just visible in the first two photographs. There is a hint of a horizontal, perhaps slightly upcurving bar tangent to the top of the 22 degree halo. This is the upper tangent arc.
https://en.wikipedia.org/wiki/Upper_and_lower_tangent_arcs It is interesting the way in which each phenomenon is dependent on a different orientation of the ice crystals.
