APOD: Unusual Light Pillars Over Latvia (2009 Jan 12)

[orin stepanek]

I have nothing to add about the pillars themselves, but there is a black bar on the left of the picture which has a defined but irregular edge. This suggests that the picture was not taken through the window of a vehicle, although it may have been taken from inside a building or under a roof of some sort. Also, the black bar on the right does not have a clearly defined edge, so I doubt it is caused by a solid object--maybe it is a shadow? I also note that there are a few stars visible above the pillars.

Could the black bar be caused by the fact that there may not be any lights there?

Orin

Actually It does look as though the picture was chopped off; maybe the camera was in a box?

Orin

[Limrickuk]

I think there is a simple explanation about the light spreading out at that level. When using radar in hot and very cold climates there are quite often layering effects caused by temperature inversion at various heights causing false images and apparant solid objects. It is conceivable that light can also be similarly affected by a temperature inversion above the ground causing the light to apparantly fill the warmer layer in this way. Hope there are others who agree

[neufer]

In response to this question (quoted below), the simple answer would be that the two pillars that visibly show the trumpets, are also the brightest ones over the two brightest lamps. The fan or trumpet itself is not as bright as is the pillar below, so the phenomenon of fanning is therefore more easily visible when the lamp i bright. I think.

As for the difference in colors, that someone pointed out earlier, the right one is obviously a high pressure mercury arc with its characteristic green/bluish white. The left one would be a high pressure sodium lamp, with a much warmer, almost coppery color. There are other mercury lamps in the picture that seem to shine bright (esp. one to the right), but without having any pillars at all. Probably they have a covering on top. For a light pillar to form, the lamp has to be open upwards.

Does anyone else wonder why the effect is only seen on two of the light pillars? Kalvin touched on it, when s/he said, "not all lights are causing creating this effect". It seems that whatever the cause, it's rather 'localized'.

Interesting image.

I think the green/bluish white & coppery color pillars are FOCUSED "evergreen" & "red rose" Xmas searchlights.

http://www.msichicago.org/scrapbook/scr ... atvia.html

<<In Latvia the Christmas celebration is know as Ziemassvetki or winter festival. The festival is a direct descendent of ancient winter solstice celebrations. A central element to Ziemassvetki is the log burning which involves groups of people dragging a log around the house during the day, burning the log all night singing ritual songs and drinking beer.

The earliest mention of a decorated Christmas tree in Latvia is found is found in legal documents from the city of Riga. In 1510 it is stated that members of the local merchant guild carried a Firtree decorated with artificial roses to the marketplace. They danced around it and then set it on fire. The reasoning behind this has been lost to history, though it may have been associated with the ancient tradition of the Yule Log.

On Christmas Eve the family gathers around the tree and sings traditional Christmas carols. Traditional foods served during this time include pork, pig's snout, pig's feet, beans, whole grains, peas and a variety of breads and rolls. Each food has a meaning: e.g. eat a pea you'll cry one day less; eat a bean one day you will mature; eat a pig's snout you will write a great deal; eat a dumpling there will be many sunny days. Later, Father Christmas may visit. He is a stern looking man dressed in gray and has a long white beard. He brings gifts for the [gneiss] children and for the [Knot D] ones he gives them stick-switches.>>

Art (pig snout eating) Neuendorffer

[wehartung]

If the light columns are due to the horizontal alignment of ice crystals, then the spread of the column into a pattern that would normally occur would indicate that the ice crystals are no longer properly aligned. This might be due to a thermal inversion or a wind shear.
William Hartung

[XLIV]

The light starts reflecting where the water starts freezing. The fan at top is water that isnt completely frozen. As the moisture completely freezes closer to the ground the ice crystals concentrate into the beam.

44

[Eleri Hamilton]

If, as suggested, the light pillars are 'just' caused by window streaking, we'd be seeing a whole lot less focus in other aspects of the picture, as well. Compare to the example picture of the city out a balcony window; yes there are light streaks, but the other items in the photo (the crane, the rooftops, etc.) are all slightly diffuse as well. In the Latvia picture, the trees are fairly crisp, and the diffusion around buildings seems to be caused by the glow of the lights, rather than any glass. Not saying it wasn't taken out a window, but the window is unlikely to be the cause.

[Dims]

I think the mechanism is follows:

1) Why are pillars vertical? This because tiny pieces of ice are oriented! Most probably they are horizontal, falling like autumn leaves.

2) Hence, if the pillars are NOT vertical, the tiny ices are NOT oriented.

Summarizing: we have calm atmospheric layer down near the ground, where pieces of ice falling horizontal and we have moving layer above it, where pieces move more and more chaotical (the higher the more).

[Caseman]

I mostly agree with pmanson, the light is reflected off crystals that are aligned horizontally. I have an alternative theory for the flaring though.
The flaring is caused by the phenomenon that newly formed icecrystals are not aligned but randomly oriented. Once created, the crystals start to fall down and will gradually align themselves. Where the flaring starts is where most of the crystals are aligned. At the "wide end" of the flare only some of the crystals are align, further above (earlier in their fall) orientation is still random and light is scattered randlomly (diffuse light, looking like cloudbase).

[parkerjh]

While I am not a meteorologist, I do have experience with aerosol scatter. The physics of this phenomenon are quite interesting. It is my conjecture that the the air volume above the lights contains ice crystals with lens like shapes. I further predict that the ice lenses form microlens arrays, or a column of lenslet arrays, each focusing the beam upward. The lenslets are also likely all oriented in the same direction (with their lens bottoms down). The column of lenslets is likely uniform in size and orientation up to the point where the pattern flairs. In this region, the lenses share a different optical prescription and allow the beam to diverge.

What we see in the photo is the side scatter of the propagated beam, much like the beam of a headlight in the fog.

What is most intriguing about this phenonmenon is the conditions that allow the ice crystals to take on these shapes and allow a uniform orientation of crystals to exist throughout the column. The conditions must be very precise to create the correct optical prescription of each crystal, and the air must be very still. Very unsual and very rare conditions.

Dr. Jack Parker
Researech Coordinator
USAF

[Dims]

The light starts reflecting where the water starts freezing.

Ah, agree! The anisotropy can also disappeared due to melting, thats right!

As the moisture completely freezes closer to the ground the ice crystals concentrate into the beam.

And this can't be true. Why crystals are collected above lights then? I think they just freezing, not concentrating. Pillars location is optical illusion.

[DocFrank]

Beautiful! I would like to posit that the cone shape formed at the top is a result of heat dispersal.
As the lights are hot at their source and the temperature of the surrounding atmosphere is very cold there should be a point at which the temperature of the beam generated is no longer to maintain cohesion and therefore dissipates into the surrounding temperature well creating the cone observed.
Any thoughts on this?

[Marc Bourget]

Could the flare at the "top" of the pillar be related to viewing angle - coupled with lens effects?

Similar to the refractive angle shown by rings?

[chadair]

The microlensing suggestion is cleaver but I don't agree and I'd like to point out some observations. First, the scattering produces a "virtual" column, and scattering takes place all along the site path. The pillars are commonly attributed to horizontal oriented ice crystals. You will also notice that the brightest parts of each column all occur along a similar elevational angle to the observer (check out a few of the beams in the background). The fans occur at an angle higher than the rest, and may only be visible on those two beams because those lights are both close and bright. If there was a bright light in the background, it too may produce a fan like beam at the same elevational angle. It is possible that these actually exist in the image and can be revealed through better image processing.

The cause of the "trumpet like" beams are likely because the meteorological conditions allow for an viewing angle that is greater than typical, and this widening of the beam is an integral behavior of the ice crystals that is seldom seen. If the fans are due to a crystal interaction at a specific height above ground level, then you would see a series of fan features at different angular heights- like a perspective drawing. I don't see this.

I'd like to point out that ice crystal morphology is strongly tied to temperature and humidity, and that crystals can change quickly with time and change quickly over space with minor temp/humidity differences. The specific crystal shape that produces the trumpet beams may be rare.

One final observation, those familiar with telescope optics may think that this fan shape looks just like a "caustic horn" in optical physics, where a focus of light rays becomes blurred off-axis.

If we knew the lens and sensor size this picture was taken with, we could begin to deduce the critical angles of reflection and test this hypothesis against other images of pillars. If multiple images from different perspectives all show the fan at the same angular height, than it is entirely an optical-scattering property, and has nothing to do with the height of fog, temperature layers, moisture-ice gradient, or wind layer.

Chad Moore, US National Park Service

[LindaTF]

It seems to me that the light not only flares at the top but is more diffuse at the bottom, slightly focused in the middle and then flares. Are the ice particles dispersed in such a way, perhaps by changes in temperature or pressure, so that they create a lens of some kind? Just an idea from on old lady who doesn't know any physics.

[Wayne]

It seems that lower levels are calm, so the hexagonal ice plates fall parallel to the ground. As we get higher, there's a slight wind so the plates are wobbling and not always parallel to the ground. This causes the pillars to spread.

[Grouchycuss]

I notice that there appears to be visible stars overhead in these pictures, which tells me, "clear sky". The frost is gathering on the tree limbs, 10F or below, and no wind. I am guessing that there is a minor temperature inversion due to the extreme cold and that the temp is higher aloft than at ground level, making the crystals disperse with altitude, thus causing the "fan" effect at the top of the pillars.

[parkerjh]

In my previous post I stated that there is likely a column or stack of horizontal lens arrays, each layer having the proper optical prescription to focus forward the light from the previous layer. I agree that the whole verical volumn contributes to the process.

The evidence that "focusing" is accuring is that there is a strong conservation of light observed along the beam recording. Indeed in portions of the beam path the light appears tightly focused. Also, If this scatter were due to random processes (random distributions of crystal size and shape) there would be an exponential fall off of energy toward the top of the photo. The vertical stack that keeps the beam tight is probably rather uniform in composition. In the flairing region the crystal sizes and shapes are probably slowly changing characteristics as you go up due to differences in temperature and humidity.

Changes in scattering intensity due to observation angle seem unlikely, since this is very wide field photo and the relative angular extents are small.

This photo looks incredibly identical to the beam pattern that laser would have traveling through fog. Lasers do not need the help of focusing, since their beams are already collimated diverge very little.

I still hold that this crystral path is optically acting like a duct for the light from the sources.

Jack Parker

[MathGeek]

Well, ice pillars are caused by flat ice crystals dangling in the air, behaving like small mirrors. The trumpet shape can indeed be explained by the wobbling proposed by Wayne. The argument is basically statistical+geometrical.
The direction in which each of the crystals points is a random vector, centered around the downward direction. The integrated effect of all these microscopic mirrors yields a "blurring" mirror. The reflection of a point source becomes smeared out to an extent proportional to the size of the fluctuations, but also to the distance between observer and the ice crystals responsible for the reflection (this is the geometry bit). Now if you're looking high up, you're seeing the reflection of the point source via ice crystals that are farther away, higher up in the atmosphere. The smearing out caused by these ones is therefore wider than for crystals closer by.

One can give a quantitative mathematical argument for this phenomenon, leading to the formula cos phi = Sqrt(1- Sin(theta)^2/Cos(alpha)^2)/Cos(theta). Here, theta is the elevation angle of the line of sight (0 if looking towards horizon, pi/2 if looking towards zenith), phi is half the angular width of the pillar, and alpha is an angle measuring how much the orientation of the ice crystals varies (0 for not at all).

If you plot the function, you find that phi is 0 when looking towards the horizon (theta=0) and becomes bigger with increasing theta. For an angle theta satisfying Sin(theta)=Cos(alpha), phi is essentially pi/2, which means the width of the trumpet has become infinite and the light becomes smeared out so widely you hardly see it anymore. You can notice this feature in the picture: the trumpet stops at a certain elevation.

If anyone likes the details of the calculation, pls reply...

[abguy4]

If you don't like the Electric Universe theory - you're not gonna like this explanation. I agree with 90% of that line of reasoning, so my explanation is based on that- here goes;
The earth's atmosphere is in a constant state of electrical imbalance with respect to the earth. This is due to the constant influx of magnetic particles flowing to the earth from the Sun. The ionosphere captures the great portion of these charged particles. Because of this, the atmosphere is constantly in a charged state - NOT just during an 'electrical storm', when the lightening makes the charged state so obvious - by discharging in a furious exchange. There are atmospheric conditions which make the atmosphere a better conductor; for instance - when it's cold and more dense, and 2) when its full of moisture. Water vapor is very ionic in nature, and therefore those molecules are an excellent conductor. Ice crystals, like most crystals, are also excellent/superb conductors. Now, with that as a background, let's look at the light columns. Light has a magnetic component. Since, (in this portion of the universe), electrical and magnetic phenomena are inseparable, (for the most part) , we can presume that light is also affected by the local prevailing magnetic and electrical atmospheric background. We have here in the picture an atmosphere that is loaded with ice crystals - excellent conductors-electrically. But, aren't the ice crystals equally distributed here? Probably. So, why would the light be attracted in an unusually high distribution straight up away from earth and towards the upper atmosphere? Could it be that; the light from each bulb is following a path of least resistance- that being the (invisible) background electrical path of the ice crystals that are already aligned (everywhere in the picture) along the straight path from earth to upper atmosphere? And also that the light is being "attracted", or "aligned", along the paths set-up by the background magnetics or electrical attractors at the moment of its conception in the white-hot filament?
Isn't a photon just an electron excited to a higher frequency? And wouldn't an electron always flow along the path of 'easiest' conductance?
Notice how elegantly and undeniably the light column spreads-out as it nears the charged cloud layer - just as we would expect the charge distribution would look - if we could see it.
Respectfully yours

[cathalcom]

What about light refraction given the density of the ice at that height? Like in a rainbow. I suggest that if the elevation of the photographer changed, the fanning would appear at the same distance no matter how much the elevation of the photographer increased?

[JustKen]

Has anyone tried to contact the photographer? We need to know more about the conditions under which the photograph was taken and especially whether it was taken through a window. I notice that one of the trees in the foreground is a bit blurry towards the top. Could a frosty window be causing both effects?

[gizmopuppy]

I saw similar photos to these Latvian Pillars on the web and asked the photographer to comment:

From Marko Riikonen:

"Tell the guys in the forum that in in your photo there is just a pillar and V-shaped 22 upper tangent arc. Both are common halos, though upper tangent arc is somewhat rarer with streetlamps.

http://www.ursa.fi/~riikonen/Rovaniemi/pages/0640.htm

shows these kind Y-shaped pillars in the background of a spotlight halo display. Same crystals all over the place, but spotlight is much better in creating halos than floodlight."

[DEEarl]

I thought I posted on this this morning, but since my posting has not shown up, I may have sent it elsewhere. Here is my second attempt.

I agree with PManson (and others now) that light pillars result from diffuse light being selectively reflected by planar ice crystals falling in calm air and thereby stabilizing in a horizontal orientation to become flat, horizontal mirrors. A consequence of this explanation is that the columns visualized are not actually vertical, but are inclined 45 degrees toward the observer. Our senses do not pick this up, as the distance is too great for binocular triangulation, and a vertical pillar seems to better fit our visual calculations. We demonstrated this during an exceptional light pillar display a few years ago (on an very cold, calm night here in Minnesota), by shining a bright spotlight in a vertical direction thinking it would create the mother of all light pillars. When we retreated a few blocks away, our pillar was invisible, as it did not include the diffuse light which would have presented the required 45 degree column of planar crystals. On the other hand, looking directly overhead, along the column of bright vertical light, revealed the column of planer crystals high into the night sky. Closer to the observer, it was even possible to estimate the number of crystals per cubic foot. Sadly, I do not recall this number, but it was surprising, to me, that the number was sufficiently small to be estimated, but still capable of a brilliant display.

So how about this? Flat crystals tumble though turbulent air, reflecting any incident light in all directions. At this point, no selecive reflection is seen, and no pillars, or other light effects, are visible. When the crystals reach the calm, lower regions, they are able to assume and maintain a horizontal orientation. It is during this transition that the funnels on top of the pillars appear. Once the crystals are fully-stablilized they will reflect a column of light in the direction of the observor. The pillars apparent width, is directly related to the degree to which the crystals are able to remain horizontal.

[aefields]

The fans don't look like Moilanen arcs. Moilanen are parabolic, aren't they? These curve the wrong way for that. With a parabolic arc the width of the fans would increase more slowly with height. The width of these increases more rapidly with height.

They do look similar to Marko Riikonen's, but they're sharper.

The fans look like the lower tangent arc in this picture http://www.atoptics.co.uk/halo/tanim4.htm They're sharper than the upper tangent arc in any of the pictures I've seen, but the way they spread is similar. But could upper and lower tangents be reversed?

[nrocekri]

pmason got to the thought before I did (time-zone differences -- feh! ). However, the solution does not require a wind aloft: if the crystals are forming in the cloud layer and then drifting down, they won't all align properly at first. The alignment interval could explain the flare at the top of each pillar. The slight defocusing in the middle could be due to a small amount of turbulence. If someone with analysis tools could check the intensity of the light at various heights (angles), that might give us a clue to the crystal refraction: there should be differences at various angles, somewhat as rainbows refract at only certain angles, no?

Of course, a pure interpretation of this concept would dictate that the pillars look like emission spectra, but I'm thinking that an ice crystal large enough to fall would have several refractions and reflections in volved, which could explain the more even distribution. If the effect depends on a large number of refractions, we'll get nothing from an intensity analysis, much as the light from many bounces down a fiber-optic cable won't show any particular focus or collimation.