The intensity pattern / distribution along the circumzenithal arc requires consideration of several effects : Fresnel's reflection & transmission amplitudes, atmospheric attenuation, chromatic dispersion ( i . e . the width of the arc ), azimuthal angular dispersion ( ray bundling ), and geometrical constraints.
12.
Both arcs are brightly coloured ring segments centred on the zenith, but in different positions in the sky : The circumzenithal arc is notably curved and located high above the Sun ( or Moon ) with its convex side pointing downwards ( creating the impression of an " upside down rainbow " ); the circumhorizontal arc runs much closer to the horizon, is more straight and located at a significant distance below the Sun ( or Moon ).
13.
Third there was a very much larger circle with also a lot of beautiful colours around the sun ( " the 46?halo " ), surrounding the other one, a bit fainter and not totally closed as the horizon was too near and the diameter of the circle too big, on which near the uppermost point an inverted part of a rainbow was visible ( " the circumzenithal arc " ), very bright and with beautiful colours.
