Thinking about the green flash

It has been a brilliant week for sunsets. As light from the Sun passes into and through the atmosphere, it slows down slightly and is bent. This bending depends on the optical density of the air (its refractive index) and varies with the density of the air layers. We could draw a diagram in which light from the Sun was unbent and traveled straight. Then we could work out when it was below the horizon and we could no longer see it. However, because of refraction and the bending, straight line rules don't work and the top of the Sun would still just be visible. This hair-splitting depends on how you choose to define "over the horizon". So in my last picture, I can argue that the Sun is actually over the horizon. At this last point, the refraction splits the light into colours as does a prism. The last colour to be seen should be blue but that is selectively scattered leaving the last colour as a green flash in perfect conditions. I thought I caught a glimpse. I am finding the explanations hard going so expect more when I've done more thinking.