Iridescence & Corona
toptics
A
Highlights
A scene by Marco Meniero at Viterbo, Italy. The sun shines through thin diffuse cloud, likely newly birthed. Surrounding the sun is an intensely bright aureole circled in turn by delicate coloured rings. A corona.
A corona is a common enough sight. Less common are the simultaneously surrounding patches of colour. Cloud iridescence.
Diffraction of sunlight by tiny cloud droplets made them both. The differences comes from the droplets themselves. Uniform sized droplets produce a corona. Clouds with changing drop size from place to place give the more disordered but beautiful pastel hues of iridescence. Why newly birthed clouds? Droplets in newly formed clouds have the same history and very similar sizes necessary for the diffraction colours not to be blurred out to white.
This close up shows less circular coronal rings merging into disordered iridescence.
