This is a YAHP (Yet Another Halo Phenomenon) post, I’m afraid, like this one, and the ones it links to.
I took the photo while flying out to Lanzarote, but I am only posting it now as I didn’t have facilities to crop and contrast-boost the photo on my phone, and I didn’t take my laptop on holiday. The white spot is a sub-sun, caused by light reflecting off the horizontal surfaces of ice crystals. The little rainbow patch to its right is a sub-parhelion, caused by light passing in and out of the sides of an ice crystal, and reflecting from the horizontal lower surface. As usual, the explanations can be found on the atoptics web site: here and here.
