Solar Corona imaged by Stefan Krivan at Manawatu, New Zealand. ©Stefan Krivan, shown with permission.

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Waves scattered from the rim of droplets or other objects like pollen are largely responsible for forming a corona.

The diagram (for simplicity) shows two series of scattered spherical waves radiating outwards from two points on a droplet rim.   In reality, waves from points all over the droplet surface contribute.

Where wave crests of the same direction overlap they combine and there is light in that direction.

Where the overlapping crests are of opposing sign they interfere, cancel each other out and there is darkness at that angle.

The overall result far from the droplet is bright light in the direction of the original light, the corona's central aureole, with surrounding bright rings.
"The corona was caused by tiny water droplets in high altitude cloud cover which diffract sunlight.   The corona size and brilliance suggests that the water droplets were quite small and were of similar size to each other.

Trying to cover the sun to view the sun coronas can be quite annoying, but it works. Fingers, buildings, trees or even the reflections of water can help with seeing the colors.   I used a native Cabbage tree and also a rose bush.   

Believe it or not, the Cabbage tree may look like a palm tree, but it is actually the worlds tallest lily & grows up to 20m tall.