Curious effect over commercial airplane wing. I suspect reflections from ice

[Ric Werme]

There's a curious image and brief video at http://spaceweathergallery.com/indiv_upload.php?upload_id=130105 showing an arc of something above the wing of a commercial flight. No flight details were reported.

Taken by Shiraishi on October 10, 2016 @ Over Japan Sea

Details:

Something like diamond dusts glitter on plane.

I saw some glittering particles on a wing of my airplane.
They aligns along an arc.
I composited the frames from a movie, and I found 2 arcs on the wing.
I do not know whether there are actually 2 arcs of ice crystals or one can see 2 arcs due to the relationship among me and the crystals and the Sun.

Sony ILCE-7S digital camera; ISO 250, F10, 1/1000s exposure, f=30mm
A composite of 132 frame from a 4.4s movie.

Content from external source

Source: https://www.youtube.com/watch?v=j4JHVEig2Tw
Video description translated:

There was something glittering on the airplane wing.
Things such as diamond dust, have been sparkling along the arc-shaped. Arc-shaped Nanoha, what are lined up that way, I do not know whether this is so in relation to the sunlight.
Thumbnail is a stack of 132 sheets of the frame of this video.

Content from external source

I suggested elsewhere that the something are ice crystals, probably plates reflecting sunlight. The orientation may be due to vortexes, turbulence, or something else.

Have people here seen this phenomenon?

The video is important, the image is a composite of the whole video and is very different. Think time lapse photo.

[Mod: added frame grab from video, below]

 

[Mick West]

Plate crystals being disturbed so they momentarily sparkle in the sun makes sense. However the arcs don't really make sense to me. There's no vortex up there above the wing. Maybe a lot closer to the window than it seems.

 

[Mick West]

I suspect SWR 161 or SWR 160




Time is given as 13:58:29 (say 14:00 for simplicity), however no indication of time zone. I suppose it would either be Zurich (hence 12:00 UTC) or Tokyo (hence 05:00 UTC)
[Edit] Timestamp is the composite image creation time on October 16, not the video time, which was on Oct 10th

 

[Trailspotter]

I think this effect is not on the wing, but on the window. This could indeed be due ice crystals formed outside or between the inside and outside glass.

 

[Mick West]

I think this effect is not on the wing, but on the window. This could indeed be due ice crystals formed outside or between the inside and outside glass.

That was my first impression. However they appear to be in focus, and the frame of the windows is not.

 

[Clouds Givemethewillies]

There's no vortex up there above the wing

There is circulation, and therefore a centrifugal force vector added to the weight vector.

 

[Ric Werme]

From the video it's clear that there are particles moving past the window. My eye says they're above the wing, my brain points out that there are very few distance clues.

They certainly appear to be outside of any place where airfoil effects dominate.

It would seem possible that the plane is flying through a volume of ice plates, all happily drifting downward and sharing the same alignment.
Could the bulk motion of air around the nose of the plane rotate some of the air mass an orient the ice plates so their reflections make an arc-like appearance?

Or, perhaps the flakes are tumbling in a fashion that reflection/refraction results in a halo effect. I don't have enough experience with that sort of phenomena argue well for or against it.

 

[Mick West]

A340 wake vortices:

Source: http://www.dlr.de/dlr/desktopdefault.aspx/tabid-10081/151_read-6937//year-all/#/gallery/9597


A340 Aerodynamic contrails:

source: http://www.airliners.net/photo/China-Eastern-Airlines/Airbus-A340-642/1398132/L
Note how it's coming up over the body just behind the wings, which could possible line up with the window

 

[Mick West]

Note I'm not suggesting it's an aerodynamic contrail. I think the floating aligned ice crystals makes more sense. The pic of the aerodynamic contrail is to show where the air flow is.

 

[Clouds Givemethewillies]

Or, perhaps the flakes are tumbling in a fashion that reflection/refraction results in a halo effect

Except there are two distinct, and different, arcs.

 

[Trailspotter]

There is a similar effect over the wing that caused by the engine nacelle strakes (nacelle chines), aka vortex control devices on the engine nacelle. They do create small vortices flowing over the wing, although in all images I've seen before, the contrails entrained in these vortices are closer to the wing surface:

Overwise, A340 with its four engines, probably has two such vortices on each side:

 

[Mick West]

A simplistic view match puts it about 5 windows back in the rear section.

 

[Mick West]

Maybe they are part of longer vortices, but we only see the parts lit by the sun?


Although there is no shadow visible on the wing top, so it would seem like the outer one should be more visible.

 

[Clouds Givemethewillies]

Maybe they are part of longer vortices, but we only see the parts lit by the sun?


Although there is no shadow visible on the wing top, so it would seem like the outer one should be more visible.

_Stead state_ they don't align themselves with steamlines, but perpendicular to their own drag, which is equal and opposite to the force moving them.

 

[Mick West]

_Stead state_ they don't align themselves with steamlines, but perpendicular to their own drag, which is equal and opposite to the force moving them.

So what do you think is happening? What air flow is doing this exactly?

 

[Clouds Givemethewillies]

So what do you think is happening? What air flow is doing this exactly?

It is difficult to argue this is steady state or quasi-steady state. What happens when they (horizontally aligned hexagonal ice crystals) come across a plane travelling at close to the speed of sound, I cannot guess, but it is the dynamic forces you would need to know, and I don't have a clue! Note however, that the vertical components of weight and centifugal acceleration are opposite over the wing, which will relatively exaggerate the horizontal component leading to more rotation, compared to that of the normal to the streamline... I think... but basically I give up!

 

[Clouds Givemethewillies]

I think we need to know where the sun is before it is worth thinking about. Very odd!

 

[Trailspotter]

I think we need to know where the sun is before it is worth thinking about. Very odd!

Second attempt. First time I got confused by the time of the photo in OP (2016:10:16 13:58:29), but this is not the time of the video. It is the time of the composite photo of 132 video frames having been assembled. The time of video is not specified, but the video itself was taken six days before, on October 10, 2016 @ Over Japan Sea.

I checked the shadows on the wing in several other videos taken aboard of a Swiss Air A340 and concluded that in the OP video the Sun was right behind the plane. This would be in an agreement with SWR161, departing Tokyo in the morning at about 10:35 local time and heading northeast over Japan Sea toward Russia. The route above the sea, however, is not straight (see above, #3), as the plane goes around North Korean and Chinese airspaces.

 

[Z.W. Wolf]

That was my first impression. However they appear to be in focus, and the frame of the windows is not.

I agree that these points of light in the two arcs are in focus and not close to the camera.

What strikes me is that we are seeing points of light with no motion blur. Let's say, for the sake of the argument, that these are ice crystals moving at a speed of 550 mph relative to the camera. That translates to 807 ft/sec - about the muzzle velocity of an army ball .45 ACP.

There are a few very short streaks here and there. It's tempting to say that they are all outside of the arcs (closer to the camera), but that's not provable. But, still, these are very short streaks. Not what you'd expect to see from a tracer bullet at this distance from the camera.

So why are we seeing points of light?

There must be some optical effect.

It looks for all the world like some strobe effect. But what could possibly cause sunlight to strobe? Or are these crystals that are flashing in the sunlight very very quickly when the sunlight is reflected/refracted just right? Are we seeing just a fraction of the ice crystals that are actually there? Just the ones that are oriented just right to reflect/refract the sunlight back to the camera? And could that mean that the arcs themselves are purely an optical effect?

 

[Clouds Givemethewillies]

I agree that these points of light in the two arcs are in focus and not close to the camera.

What strikes me is that we are seeing points of light with no motion blur. Let's say, for the sake of the argument, that these are ice crystals moving at a speed of 550 mph relative to the camera. That translates to 807 ft/sec - about the muzzle velocity of an army ball .45 ACP.

There are a few very short streaks here and there. It's tempting to say that they are all outside of the arcs (closer to the camera), but that's not provable. But, still, these are very short streaks. Not what you'd expect to see from a tracer bullet at this distance from the camera.

So why are we seeing points of light?

There must be some optical effect.

It looks for all the world like some strobe effect. But what could possibly cause sunlight to strobe? Or are these crystals that are flashing in the sunlight very very quickly when the sunlight is reflected/refracted just right? Are we seeing just a fraction of the ice crystals that are actually there? Just the ones that are oriented just right to reflect/refract the sunlight back to the camera? And could that mean that the arcs themselves are purely an optical effect?

I got very confused, and worked out that they were rotating at something like 2000rpm. I decided I needed a little lie down.
EDit:
When I worked out that they were falling upwards, the reflections were from the side faces, which were also aligned relative to the flight path, and that the two arcs were probably 30 degrees apart, I started worrying about men in white coats..

 

[Ray Von Geezer]

I agree that these points of light in the two arcs are in focus and not close to the camera.

What strikes me is that we are seeing points of light with no motion blur. Let's say, for the sake of the argument, that these are ice crystals moving at a speed of 550 mph relative to the camera. That translates to 807 ft/sec - about the muzzle velocity of an army ball .45 ACP.

There are a few very short streaks here and there. It's tempting to say that they are all outside of the arcs (closer to the camera), but that's not provable. But, still, these are very short streaks. Not what you'd expect to see from a tracer bullet at this distance from the camera.

So why are we seeing points of light?

There must be some optical effect.

It looks for all the world like some strobe effect. But what could possibly cause sunlight to strobe? Or are these crystals that are flashing in the sunlight very very quickly when the sunlight is reflected/refracted just right? Are we seeing just a fraction of the ice crystals that are actually there? Just the ones that are oriented just right to reflect/refract the sunlight back to the camera? And could that mean that the arcs themselves are purely an optical effect?

Is it possible that the crystals aren't actually moving in those arcs, but are passing through the light from a reflection off part of the plane and the arcs are the shape of the reflection? A bit like if you filmed dust motes in headlights and then made a composite of all the frames, I think they'd look like dust was "following" the shape of the beam.

The crystals do look like they're moving in those arcs, but could that just be the effect of the camera as the reflection illuminates the crystals?

Probably not, just an idea

Ray Von

 

[Trailblazer]

I agree that these points of light in the two arcs are in focus and not close to the camera.

What strikes me is that we are seeing points of light with no motion blur. Let's say, for the sake of the argument, that these are ice crystals moving at a speed of 550 mph relative to the camera. That translates to 807 ft/sec - about the muzzle velocity of an army ball .45 ACP.

There are a few very short streaks here and there. It's tempting to say that they are all outside of the arcs (closer to the camera), but that's not provable. But, still, these are very short streaks. Not what you'd expect to see from a tracer bullet at this distance from the camera.

So why are we seeing points of light?

There must be some optical effect.

It looks for all the world like some strobe effect. But what could possibly cause sunlight to strobe? Or are these crystals that are flashing in the sunlight very very quickly when the sunlight is reflected/refracted just right? Are we seeing just a fraction of the ice crystals that are actually there? Just the ones that are oriented just right to reflect/refract the sunlight back to the camera? And could that mean that the arcs themselves are purely an optical effect?

If the particles are spinning/tumbling rapidly then you would only see a flash when the face is aligned "just right", similar to the appearance of "diamond dust" ice crystals (as the original description states).

 

[Trailspotter]

I agree that these points of light in the two arcs are in focus and not close to the camera.

I am not so sure, despite what the author of the video says:

…I do not think something happened between the panes of window, because the panes are too close to be focused well in this photo.
The distance between the winglet and me was about 25 m (This plane is A340-300). And this photo was taken by F10 and f=20mm in APS-C (30mm-equivalent).
Thus, the depth of field is 1.7 m to infinity. I set AF at the winglet. Even if the best focus was set at the middle of the wing, the depth of field would be 1.5 m to infinity. So, anything between the window panes could not be resolved. Please note that the window edge was blurred by out of focus. If anything between panes could be resolved, the scratches on panes could be also resolved (however, they can not be seen).
Subjectively speaking, I saw the particles in the air outside.

Content from external source

I cannot see these arches being a part of airflow outside, they appear too high above the wing surface. I still think they can be in between the window panes. The points of lights are not necessarily in focus, they can be just tiny ice microcrystals, caught in air convection between the panes.

If the deduction in my previous post (#18) correct, the video was made in the beginning of the flight. As the plane reached the cruising altitudes with outside temperatures about or below -40°C, the temperature of air between the window panes dropped and eventually got below the freezing point. I think that in the beginning, the forming ice crystals were tiny, many and suspended in the air. Some of these crystals would later stuck to the glass and grow bigger for the expense of others, to the annoyance of fans of aerial photography, like myself.

The sun was behind the plane at the time, but probably would still illuminate the window panes, sending reflections from these micro crystals toward the camera. The air convection between the window panes could have arranged them in the observed two arches.

At least this is a hypothesis that I can test when taking the next flight.

 

[Clouds Givemethewillies]

I am not so sure, despite what the author of the video says:

…I do not think something happened between the panes of window, because the panes are too close to be focused well in this photo.
The distance between the winglet and me was about 25 m (This plane is A340-300). And this photo was taken by F10 and f=20mm in APS-C (30mm-equivalent).
Thus, the depth of field is 1.7 m to infinity. I set AF at the winglet. Even if the best focus was set at the middle of the wing, the depth of field would be 1.5 m to infinity. So, anything between the window panes could not be resolved. Please note that the window edge was blurred by out of focus. If anything between panes could be resolved, the scratches on panes could be also resolved (however, they can not be seen).
Subjectively speaking, I saw the particles in the air outside.

Content from external source

I cannot see these arches being a part of airflow outside, they appear to high above the wing surface. I still think they can be in between the window panes. The points of lights are not necessarily in focus, they can be just tiny ice microcrystals, caught in air convection between the panes.

If the deduction in my previous post (#18) correct, the video was made in the beginning of the flight. As the plane reached the cruising altitudes with outside temperatures about or below -40°C, the temperature of air between the window panes dropped and eventually got below the freezing point. I think that in the beginning, the forming ice crystals were tiny, many and suspended in the air. Some of these crystals would later stuck to the glass and grow bigger for the expense of others, to the annoyance of fans of aerial photography, like myself.

The sun was behind the plane at the time, but probably would still illuminate the window panes, sending reflections from these micro crystals toward the camera. The air convection between the window panes could have arranged them in the observed two arches.

At least this is a hypothesis that I can test when taking the next flight.

Some of the larger sparkles, mainly outliers, show short, horizontal streaks. Difficult to explain with windows..

 

[Trailspotter]

Some of the larger sparkles, mainly outliers, show short, horizontal streaks. Difficult to explain with windows..

Do you refer to the composite image (which can be misleading), or individual frames?
Anyway, there could have been a few ice crystals outside the window (and not in the arches).

 

[Clouds Givemethewillies]

Do you refer to the composite image (which can be misleading), or individual frames?
Anyway, there could have been a few ice crystals outside the window (and not in the arches).

The composite image. "Anyway, there could have been a few ice crystals outside the window (and not in the arches)" Clutching at straws there!

 

[Mick West]

The points of lights are not necessarily in focus, they can be just tiny ice microcrystals, caught in air convection between the panes.

If we see a point of light. Then that means it is in focus. Watch the upper right out-of-focus blob on the window in the video.


That is on the window, it moves with the window. no matter how small a point of light was, it's going to have the same circle of confusion. It cannot remain a point.

I 99.999% agree wth Shiram's assessment that it was outside the window.

[Note Shiram = Masayuki Shiraishi, the image is labeled Shiraishi, then he comments as Shiram]

 

[Trailblazer]

The "rapidly tumbling ice crystals" explanation makes the most sense to me. As seen in the composite image, there are some that show horizontal streaks of varying lengths. That would be consistent with a particle that was shaped to reflect light over a wider angle, so it would still show up for a longer period as it tumbled.

I circled a couple of them here. These two in particular show brighter dots which could be the optimum reflection angle. (Or perhaps another particle that just happens to be in front of them.)

 

[Trailspotter]

Watch the upper right out-of-focus blob on the window in the video.

Are you sure this blob is on the window and not a reflection of something inside the plane and behind the camera? Also, what do you think is the moving pale "shadow" on the top of the frame that slides from left to right?

 

[Mick West]

Are you sure this blob is on the window and not a reflection of something inside the plane and behind the camera?

It seems to move perfectly in sync with the window frame on the left side. It also seems to dark to be a reflection.

Also, what do you think is the moving pale "shadow" on the top of the frame that slides from left to right?

Looks a little like a cloud, but I suspect it is actually the reflection of the sleeve of someone walking by, likely a cabin crew member.

 

[Trailspotter]

Here is another possible explanation of the arches:

Their ends are not over the wing, but on its leading edge. The arches may correspond to a zone where the ice crystals formed due to the pressure drop on the wing will grow to a visible size. The shape of this zone may be determined by the positions of engines under the wing, particularly, the outer ones.

Presumably, there were marginal conditions for an aerodynamic contrail with the ice crystals sublimating behind the wing.

 

[Mick West]

Here is another possible explanation of the arches:

Their ends are not over the wing, but on its leading edge. The arches may correspond to a zone where the ice crystals formed due to the pressure drop on the wing will grow to a visible size. The shape of this zone may be determined by the positions of engines under the wing, particularly, the outer ones.

Presumably, there were marginal conditions for an aerodynamic contrail with the ice crystals sublimating behind the wing.

But then why are there none visible behind the arch. The ice crystals would have to spring into existence and then instantly vanish. Otherwise you'd be seeing them extend in a sheet to the right of the image.

 

[Trailspotter]

But then why are there none visible behind the arch.

There quite a few white dots behind the arches (in the full-size composite image in OP).

The ice crystals would have to spring into existence and then instantly vanish. Otherwise you'd be seeing them extend in a sheet to the right of the image.

This is the point. The conditions are marginal, so the ice crystals are short lived. They form in the pressure drop zone above the wing and vanish behind it. The arches in the composite image are the area of the maximum probability of ice crystals.

Edit:
Here, for illustration, are a couple of flickr photos of the water condensation over the A340 wing, showing a somewhat similar wavy (arched?) edge:
Airbus A340 Contrail by Chris Turner, on Flickr
Iberia A340-300, Winged Iridescence by Roberto Figueredo Simonetti, on Flickr

 

[Masayuki SHIRAISHI]

Hello, colleagues,
This is Masayuki Shiraishi, the person himself who took the photos and movie of something glittering over a plane wing last year, just one year ago.
I've considered the phenomenon but I have no idea.
Yesterday, I found this thread and I knew that you all had discussed the phenomenon.

If this thread is still open, I will add some information.

The flight was LX161 of Swiss International Air Lines, NRT (Japan) to ZRH (Switzerland), as Mick mentioned (correct!).
The date of flight was October 10, 2016; and the time that the phenomenon appeared was 10:48 UTC+9.
It was about 20 minutes later from the departure. Typical departure time is 10:25 UTC+9.
I think it was over the Japan Sea, but at that time I could not see the sea because clouds spread under the plane.

At first I noticed that something glittering over the wing by naked eyes.
It was apparently outside of the plane.
Then I tried to take some photos of them, however, glitter was too quick to be captured a single shot.
So I took a short movie so that I can stack the multiple frames from the movie later.
This phenomenon continued only one or two minutes.
After that, a vapor line appeared from the wing tip (10:49), see the following photo.
After the glitter disappeared, the wing tip vapor line continued for several minutes.
Later I found that there were 2 arcs over the wing, by the stacked image.
On flight, I saw only one glittering arc (larger one). The other one could not be recognized by naked eyes.

My seat was 36K, the right window-side, a little rear of the right wing.
(I love taking photos outside of plane's window; terrain, clouds, dusk and dawn, night stars, airplane glories...)
A rough estimation of the position, direction, and sunlight direction was shown below.

he
So, the line of sight was approximately opposite of the Sun.
If they are flying ice crystals, I think the angular condition among the Sun, crystals, and me is also related.
They will reflect sunlight within a narrow path flaring to me, like an Iridium flare.

Some people suspect something on double window panes, but I don't think so.
The panes are too close to be resolved in these images.
This photo and movie were taken in F10, and the distance between the wing tip and me was about 25 meters (A343-300). I set auto-focus at the wing tip. In this case, the depth of field is 1.7 meters (near) to infinity (far).
So, anything between window panes and any scratches on window panes can not be resolved.
And anything 1.7 meter or farther from me could be in focus.
This is just as Mick mentioned.

This thread contains interesting discussion.
If they are ice crystals, why is it rare...?
I searched for similar phenomena's photos, reports, and descriptions, but I could not find...

I'm sorry for my poor English.
Best regards,
Shiraishi

 

[Clouds Givemethewillies]

Do you know the temperature, or altitude? From the time of flight, and post #2, it may have reached 32,000ft.
Great capture of an unusual event BTW!

 

[Mick West]

If they are ice crystals, why is it rare...?

The loose theory above is that it's ice crystals that momentarily get aligned to reflect or refract the sun as they get swept up in a laminar (parallel) flow (https://ja.wikipedia.org/wiki/層流 ) that tilts them from a pre-existing orientation (probably horizontal) through an orientation that reflects the sun.

Random sparkles outside the arcs seem to match this theory.

It would be rare for the same reasons that certain types of solar halo are rare. It requires a certain type of ice crystal, and a certain sun angle. It's not really clear what is happening, but I wonder if it might be something that could be duplicated in simulation.

 

[Clouds Givemethewillies]

At a guess the flashes were caused by previously horizontally aligned trigonal ice plates around 0.5mm dia.

 

[Ross Marsden]

Les Cowley of "Atmospheric Optics" distributes a program called HaloSim.
You can simulate halos by controlling several parameters including the crystal shape.
Maybe the ray tracing engine could be employed to simulate the halo featured in this thread.

[edit to correct spelling]

 

[Mick West]

Les Cowley of "Atmospheric Optics" distributes a program called HaloSim.
You can simulate halos by controlling several parameters including the crystal shape.
Maybe the ray tracing engine could be employed to simulate the halo featured in this thread.

I had the same thought, I've emailed Les to see what he thinks.

 

[Z.W. Wolf]

I'd like to know what the shutter speed was.