Total Eclipse Corona

The previous OPOD prompted Steve Mattan to send these images of the 2010 total solar eclipse taken from an atoll in French Polynesia.

The clouds broke some fifteen minutes before totality and here the eclipsed sun with diamond ring is surrounded by a corona/iridescence.  Droplets in the remaining thin cloud
diffract the sun's light to form the colours.

Images ©Steve Mattan, shown with permission

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Shadow bands from higher up atmospheric density fluctuations are projected onto lower cloud. Usually they are seen on the ground but here an intermediate level cloud layer is acting as a translucent screen.

Corona or Iridescence?

Both are produced by diffraction from individual cloud droplets.   Scattered waves radiate outwards from all points on the drop surface. Where they overlap they interfere. Waves in-phase reinforce and waves out of phase are destroyed.

When all the drops are of nearly the same size the overlapping patterns from individual drops are not blurred out and there is a ringed corona. When the size changes from place to place in a cloud the pattern and colours become more irregular. This gives iridescence.