Puffball Spore Corona

A reminder of the golden days of Autumn. Rafael Schmall saw this corona unusually created by the spores from puffball mushrooms. “We were in the beautiful forest near Kaposfo [Hungary] when I accidentally kicked over a "Pöfeteg" [puffball mushroom]. The released spores created a very dense fog and when I looked through it there was a multi-ringed corona. Later on we found a few old mushrooms and summoned more coronae!
    ©Rafael Schmall, shown with permission
The cloud from the disturbed puffball mushroom is special in that the tiny spores are all of the same size. At right the scanning electron micrograph by Alex Hyde (Alex Hyde Photography) shows spores from Calvatia gigantea. The prickly spheres are a mere 3.7 micron ( 0.004mm ) diameter.

Monosized particles are ideal for producing coronae. Apart from cloud and mist droplets, pollens are well known sources. These coronae from mushroom spores are possibly a first.

This schematic shows scattering from only two surface points. The circular pattern results when the whole surface participates.

Atmospheric
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The corona of a central aureole surrounded by several coloured rings is a diffraction pattern. The spores, or whatever small particles, scatter incident light in all directions as outgoing spherical waves. The spreading waves overlap constructively or destructively. In the far field, directions where the overlapped waves are in phase there is light, completely out of phase directions yield darkness.

The angular size of the resulting corona depends on the diameter of the source particles. Smaller particles give larger coronae – Hence the desirability of monosized particles for the sharpest coronae with many rings.

Analysis of Rafael Schmall’s images gives a spore diameter of 4.2 micron, very much in the range of those from puffball mushroom varieties.