I did some searching and found
this helpful article about lunar coronae by Les Cowley et al.. Here I give a brief summary:
A lunar corona results from diffraction of moon light off water droplets. It is different from a rainbow in that the latter results from reflection, refraction, and dispersion in water.
Whether diffraction or refraction dominates depends on the ratio between the wavelength in question and the size of the droplet. Visible light has a wavelengths of about 500 nm. Raindrops have sizes of about 2mm, much larger than the wavelength of visible light, and reflection and refraction dominate (resulting in rainbows). The droplets causing the luna corona have a size of about 10micro meters, wich is only about a factor of 10 larger than the wavelength. Hence, diffraction plays a more dominant role.
There are different levels of rigour when it comes to diffraction calculations. As a first step (
also mentioned by Neufer) on can use Frauenhofer far-field diffraction. In this limit, the diffraction pattern from a single droplet is the the same as that of a disk of the same size (Babinet’s theorem). The pattern is then given by the Airy disk.
When all drops have the same size, the resulting corona looks like today’s APOD. When the drops size has a narrow distribution the corona can be noncircular. An extreme case is
iridescence.
A more general approach, that is needed when the drop size is “small”, is Mie scattering theory. Computer codes can be used to solve the equations and yield the correct corona properties. The article gives several examples.
(end of summary)
I haven’t found a reference to Mie theory yet, but from the above article, Mie theory is a solution of the classical Maxwell equations and does not involve QM in any way. It is a general Ansatz for (classical) scattering theory, but requires computers to solve effectively. If it successfully describes lunar coronae I don't understand why one would want to say that they are a QM phenomenon. But this does not mean that all scattering problems can be described by classical physics. As a rough estimate, I would say that classical scattering theory breaks down once the wavelength of light becomes comparable to the size of molecules and atoms.
I did some searching and found [url=http://dx.doi.org/10.1088/0031-9120/40/1/004]this helpful article about lunar coronae by Les Cowley et al.[/url]. Here I give a brief summary:
A lunar corona results from diffraction of moon light off water droplets. It is different from a rainbow in that the latter results from reflection, refraction, and dispersion in water.
Whether diffraction or refraction dominates depends on the ratio between the wavelength in question and the size of the droplet. Visible light has a wavelengths of about 500 nm. Raindrops have sizes of about 2mm, much larger than the wavelength of visible light, and reflection and refraction dominate (resulting in rainbows). The droplets causing the luna corona have a size of about 10micro meters, wich is only about a factor of 10 larger than the wavelength. Hence, diffraction plays a more dominant role.
There are different levels of rigour when it comes to diffraction calculations. As a first step ([url=http://asterisk.apod.com/viewtopic.php?t=34872#p244566]also mentioned by Neufer[/url]) on can use Frauenhofer far-field diffraction. In this limit, the diffraction pattern from a single droplet is the the same as that of a disk of the same size (Babinet’s theorem). The pattern is then given by the Airy disk.
When all drops have the same size, the resulting corona looks like today’s APOD. When the drops size has a narrow distribution the corona can be noncircular. An extreme case is [url=http://apod.nasa.gov/apod/ap140708.html]iridescence[/url].
A more general approach, that is needed when the drop size is “small”, is Mie scattering theory. Computer codes can be used to solve the equations and yield the correct corona properties. The article gives several examples.
(end of summary)
I haven’t found a reference to Mie theory yet, but from the above article, Mie theory is a solution of the classical Maxwell equations and does not involve QM in any way. It is a general Ansatz for (classical) scattering theory, but requires computers to solve effectively. If it successfully describes lunar coronae I don't understand why one would want to say that they are a QM phenomenon. But this does not mean that all scattering problems can be described by classical physics. As a rough estimate, I would say that classical scattering theory breaks down once the wavelength of light becomes comparable to the size of molecules and atoms.