Interesting Refraction/Diffraction phenomenon [Subhorizon halos: Sub-sun, Sub-sundog]

justanairlinepilot

Senior Member.


[Full sized images attached]

Can anyone help me out with describing the why this particular shape takes place? I've been flying for 27 years and have only seen this phenomenon twice, all within a month (coincidentally).

Details...
Both photos were taken at around 35,000 feet. One was in Mississippi, the other was over New York State somewhere. Keep in mind the window is about 2.5 inches thick of laminated poly. If there are other details missing I will be more than happy describing what I can.

I understand the meteorological term, "sun dog" so don't bother with that.
 

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Mick West

Administrator
Staff member
Sun dog.

Just kidding, but the first photos does look like a pair of sun dogs, with the difference being they are not next to the sun, but are centered on what looks like a reflection or refraction of the sun.

The second photo shows the same thing, but without the "sun dogs" on the side. My suspicion would be that the bright spots in the middle are actually refractions of the sun, and spots on the side of the first image are actually refractions of sun dogs.

Are there any more photos, wider angle?
 

justanairlinepilot

Senior Member.
unfortunately it's just my iphone 5. Keep in mind I'm traveling at just over 500 mph, but that seems irrelevant. This photo op only lasted about 30 seconds.

yes, maybe it's just a reflection of a refraction? I find it very interesting.

My question is why? Why does it pose itself in this image? Why not some other image? It is consistently the same shape/image.

Maybe it's as simple as asking why a rainbow looks the way it does...but so far, I haven't found anyone able to explain what I'm asking.
 

mrfintoil

Senior Member.
My question would be if the bright spots in the centre of the image was refracted on the windscreen or in the clouds far behind?
 

Mick West

Administrator
Staff member
unfortunately it's just my iphone 5. Keep in mind I'm traveling at just over 500 mph, but that seems irrelevant. This photo op only lasted about 30 seconds.

yes, maybe it's just a reflection of a refraction? I find it very interesting.

My question is why? Why does it pose itself in this image? Why not some other image? It is consistently the same shape/image.

Maybe it's as simple as asking why a rainbow looks the way it does...but so far, I haven't found anyone able to explain what I'm asking.

Did it seem to be in the window, or in the air/clouds? If you moved you head, would the spot move relative to the clouds?

What plane is it? The geometry and composition of the window will play a large part here. Also being laminated there might be angles that lead to internal reflection that give this result. It is very odd.

Is the window polarized?
 

justanairlinepilot

Senior Member.
It's a CRJ-900. It definitely seems to be in the clouds but who knows. The windows are really thick and laminated. The wind screen has UV protection but I'm not sure if it is polarized. We are unable to wear polarized sunglasses tho. If you do it messes with the glass on the instruments and you see rainbows in the windows, so maybe they are.
 

solrey

Senior Member.
Those are Sub-Horizon Arcs; Sub-Sun and Sub-Parhelia (Sub-Sundog). Awesome shots, btw.

http://www.atoptics.co.uk/halo/subhor.htm


Halos beneath the sky. A subsun, sub parhelia, subparhelic circle and a subcircumzenithal arc shine below the horizon. Continuations of 'ordinary' arcs go beneath the horizon also. Fisheye simulation centered on the horizon, sun 10° high.

Imagine a halo display mirrored in a lake. Subhorizon halos are similarly formed except that the mirroring is inside the very crystal making the halo. An extra reflection from a lower horizontal face produces the subhorizon counterpart of an ordinary plate crystal halo.

No multiple scattering or reflection by separate crystals is needed.

Subtleties of the refraction and ray paths make subhorizon arcs very similar to but not identical to their above horizon counterparts.

Look for subhorizon halos from aircraft, hills or mountains. Sometimes they can even be seen in snow and ground frosts.
Content from External Source
 

justanairlinepilot

Senior Member.
That is exactly what I was looking for, thanks a lot.


Those are Sub-Horizon Arcs; Sub-Sun and Sub-Parhelia (Sub-Sundog). Awesome shots, btw.

http://www.atoptics.co.uk/halo/subhor.htm


Halos beneath the sky. A subsun, sub parhelia, subparhelic circle and a subcircumzenithal arc shine below the horizon. Continuations of 'ordinary' arcs go beneath the horizon also. Fisheye simulation centered on the horizon, sun 10° high.

Imagine a halo display mirrored in a lake. Subhorizon halos are similarly formed except that the mirroring is inside the very crystal making the halo. An extra reflection from a lower horizontal face produces the subhorizon counterpart of an ordinary plate crystal halo.

No multiple scattering or reflection by separate crystals is needed.

Subtleties of the refraction and ray paths make subhorizon arcs very similar to but not identical to their above horizon counterparts.

Look for subhorizon halos from aircraft, hills or mountains. Sometimes they can even be seen in snow and ground frosts.
Content from External Source
 

BigTBoom

New Member
Besides the image solrey cites, the site he mentioned has an almost exact duplication of the display in question. They are a product of internal reflection and orientation of the same ice crystals.

http://www.atoptics.co.uk/halo/subpars.htm



"Subparhelia ray paths. Rays enter and leave oriented plate crystals through side faces inclined at 60° to each other. They differ from ordinary parhelion rays in that they are totally internally reflected by the lower horizontal face. They leave the crystal in an upwards direction and so the subparhelia appear to be below the horizon.

These reflections are quite sufficient to explain subparhelia. It is not necessary to invoke multiple scattering from clouds of ice crystals."
 
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