Iridescence or bits of sun corona?

[Ramona Edwards]

I love looking for colors in the sky!  I was wondering how a cloud spotter can tell the difference between iridescent clouds and partial sun coronas, though?  Maybe you can only see the sun corona if it is full?  These photos show layers of color that are quite distinct in progression. I have assumed they are iridescent clouds, but I just started wondering about the difference…
Thanks!

Ramona

[Hans Stocker]

That is a nice question Ramona. i will try to annswer it.

In fact the colors of a corona and the colors of an iridescent cloud are both caused by the diffraction of light by small particles or tiny water droplets. When the droplet or particle sizes are varying a lot the pattern will be rather chaotic. In the case of a corona the particles have to be rather uniformly sized to give the regular pattern of rings. The smaller the size of the water droplets is, the larger the corona is. And when the sizes of the droplets are (almost) everywhere the same, the pattern of a corona is symmetric and circular.

Here is an example of a partial corona Solar corona and iridescence . Where the pattern becomes more chaotic it is named iridescence.

Here is an example from the gallery of a corona with very irregular rings showing the differences in sizes of the (water) particles that cause the diffraction:  Irregular rings

So in my opinion there is not much difference between iridescent clouds and a partial corona except that a corona is a more specific appearance of iridescence surrounding the sun or moon. So the images you posted show me a corona and iridescence as well. The rule of thumb I use, is that a corona does not need to be a full circle to be a corona and that iridescence becomes a corona when it is somehow (partly or fully) encircling the sun or moon. I hope you like it. Any other opinions are welcome btw.

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