Starship Asterisk*

This thread is meant for discussion of http://apod.nasa.gov/apod/ap090112.html titled "Unusual Light Pillars Over Latvia" that appeared (will appear) on APOD on Monday, 2009 January 9. Thoughtful comments and ideas about the fan shaped tops of the pillars are encouraged. This is another attempt to use the collective intelligence of APOD readers as a "problem solving engine."

- RJN

RJN wrote:Monday, 2009 January 9

Monday, 2009 January 12

Hello RJN,

It is tempting to steal APOD's thunder by posting a pic ahead of schedule but I don't think it fair, nor do I have any inkling as to the cause. Ice crystals reflecting ground lighting perhaps; sort of like a ground-based Gegenschein? As to the fanning (which is your real question after all) one (me) could suggest a temperature/density gradient over a few hundred feet above the concentrated light column.

This idea probably isn't even close to the collective intelligent APOD community's conclusion but it's all I've got!

astrolabe wrote:It is tempting to steal APOD's thunder by posting a pic ahead of schedule but I don't think it fair, nor do I have any inkling as to the cause. Ice crystals reflecting ground lighting perhaps; sort of like a ground-based Gegenschein? As to the fanning (which is your real question after all) one (me) could suggest a temperature/density gradient over a few hundred feet above the concentrated light column.

This idea probably isn't even close to the collective intelligent APOD community's conclusion but it's all I've got!

I agree, but which will it be? The red pillar, the blue pillar, or both? Beautiful pictures!

Tangent arcs, Moilanen arcs, or Parry arcs? Or HAARP?

I haven't a clue, but from what I've seen, I vote for reflected Parry arcs, or something similar. Definitely ice crystals reflecting artificial ground lighting.

Error 404. So i cant see the picture.

Doum wrote:Error 404. So i cant see the picture.

Not there yet. I googled it elsewhere. Try after midnight EST.

This may be simplistic, or wise, I don't know. It appears to me that the beams of the lights converge at one point, and then cross over and spread - just before the ice crystals run out. Thus I think it is simple, similar to phenomena I have witnessed with theater and stage lights, in or outdoors.

Is there a prioce for thw inning asnwer?

Lou

SpaceWeather.com, January 2, 2009, Mystery Pillars

Many people have seen light pillars. They appear during winter when city lights shine upward into the icy air. Reflections from plate-shaped crystals spread the light into a vertical column: examples.

Truhin's pillars, however, are not the ordinary kind. Even two leading experts in atmospheric optics can't quite figure them out: "These pillars are mysterious," say Les Cowley and Marko Riikonen. "They have unexplained curved tops and even curved arcs coming from their base. Arcs in rare displays like these could be from column crystals to give parts of tangent arcs, others could be the enigmatic Moilanan arc or even the recently discovered reflected Parry arc. We do not know, so take more photos on cold nights!"

The tops of the "unusual light pillars over Latvia" remind me of pictures of the atmospheric "sprites", which form high above the lightning discharges themselves.

Maybe the fanning out of the light is related to the focused section of the pillar just below the "fan out" and the broader, more diffused light nearer the ground. I realise that I've introduced several more unexplained phenomena, rather than explain one. Sorry; but maybe they are related, and one theory explains all.

Whatever, I'm horrified by the amount of light pollution.

I'm trying to think through the optics of this image... and I have more questions than answers.

The lights aren't pointed upward, so the "columns" presumably aren't actually columns per se, but are instead a lensing effect of the ice crystals between the light and viewer -- like lens flare. The fact that the columns are so bright over their full length, rather than scattering quickly, tends to reinforce that guess.

Assuming that to be true, the question is not just why the column broadens at the top, but why we're getting this flare only in the vertical direction and specifically upward. I'd like to know more about exactly how the photo was taken -- I know we're told it was with "an ordinary camera", but the cut-off upper right corner suggests it was shot through some intervening window which may be contributing its own effects (or have snow/frost on its surface which is doing so). And I'm wondering whether it was really centered in the lens as shown or was farther off-center and has been cropped.

HI

I THINK THE FAN OUT AT THE TOP END OF THE PILLARS ARE A NATURAL BEHAVIOR OF THE LIGHT ITSELF. IT IS LIKE WHEN THE LIGHT TRAVELS THROUGH CRYSTALINE SUBSTANCES OR MATERIALS LIKE A OPTIC FIBER CABLE OR A PRIZM (REMEMBER MICRO CRISTALS BEHAVE LIKE PRIZMS). IF YOU LOOK CLOSELY THE PHOTO, YOU WILL NOTICE THAT THE PILLAR IS NOT STRAIGHT, AT THE BASE IS THICK, THEN AT THE MIDDLE IS NARROW AND THEN THE LIGHT SPREADS OUT LIKE A SINE WAVE. I THINK THE PATTERN GOES INFINATE BUT WE CAN'T SEE IT. EVEN LASER LIGHTS SPREADS OUT OVER LONG DISTANCES.

THE DIFFERENCES IN COLOR RESPONDS TO THE SOURCE OF THE LIGHT IN COMBINATION WITH THE PRIZM EFFECT, MERCURY VAPOR LIGHTS ARE SOMEWHAT BLUEISH/WHITE AND HPS LIGHTS (HIGH PRESSURE SODIUM) ARE REDDISH OR YELLOWISH.

PEDRO M RIVERA
PONCE, PUERTO RICO

In response to loujudson, the simplest answers are often the correct ones, you just may be right. My own thoughts on this are light interference. There is more ambient light on ground level, dissapating as one goes higher. It's my thought that as these lights reach higher there is less light to interfere. With a constant amount at lower levels one would get a straight beam, but as the interference lessens, a cone would begin to appear, reflecting off neighboring ice crystals until a wide spread diffusion occurs. If you look at the lights in the background they seem to be less focused beams and more of a spread out light, not coning possibly indicating that it is the local light itself causing the phenomenon. Just a thought.

I also think it's a result of a temperature layer, where the upper layer changes the composition of the ice crysals and causes the light beam to fan out. Perhaps there may be records that indicate if temperature layers is common in the area. Perhaps even for that particular time.

My guess would be that the ice acts as a prism somehow.

That or the light isn't actually fanning out but it's just an optical illusion, like the light refraction on the surface of water; making something in the water look angled from where it actually is under the water.

I am guessing that the ice crystals are forming relatively close to ground level and they only reach sufficient size to align in a way as they fall that reflects light in the 'pillars' at the height demonstrated in the photo. I have never seen such dramatic pillars but I have seen fairly heavy and sustained snowfall while the sun or moon shines and with no apparent cloud in sight. This happens often in locations where the air is very cold and a nearby body of unfrozen water (in my case it is Lake Superior) has saturated the near ground layers of the atmosphere with humidity.

Since the lights are non-directional, but causing a line of light, could it be because the ice crystals are all being blown on the same plane, so they only reflect in one direction? Then assuming that may be true, is it possible that different wind velocities at different elevations would cause a greater diffusion of light at different points along the pillar?

Could it be that the crystals in the sky at the lower level are in a cloud form thus creating (if viewed from above), a gaseous lens. As the light travels upward, the increasing altitude lowers the pressure of the cloud of crystals and helps create a curvature of light. I also think the curvature thats formed, starts to peak out as the density of the cloud of crystals starts to decrease as the altitude increases at a certain point.

If you used a rocket nozzle, there is a combustion chamber, a converging section and a diverging section. I used the same the process as a rocket, the combustion chamber would be the tightly condensed cloud of crystals, the converging section would be the decrease in density, and the diverging section is the final product or in this case a curvature of the beam of light.

A good experiment for this would be compacting cloud crystals in a chamber or box and have different pressure levels at certain heights, and the density of the cloud would start to decrease as the height increases. If the light beam doesn't form a curve, than it could mean that the curve doesn't form at lower height levels and would need a greater distance to travel in order for the curve to come into place.

The black bar on the right hand side of the picture suggests that this picture may have been taken from the inside of a vehicle, the black bar on the right being the support pillar between the front and rear seat. The streaks look like they are on the back seat window, streaks that are caused from rolling the window up and down over time leaving "rub" marks on the glass.

I'm no expert, but here's my guess:

Light pillars happen when light from the source is reflected down (or up) off the flat surface of "plate-shaped" ice crystals to the observer. They only happen when the crystals are oriented mostly horizontally, and that happens when they're falling in calm air (like a leaf falling). Maybe in this case, there's some wind higher up and it's calm lower down, and the fanout of the light pillars happens near the boundary between calm air and stirred-up air. The crystals near the boundary would tend to be close to horizontal but as you get higher into the wind, their orientations are more dispersed, so the reflections would be more spread out from the vertical line.

It looks to me like the ice crystals behave like any other fog, maintaining a fairly consistent density up to a certain height. At the top of the fog, the density of the fog (as well as the ability of its ice crystals to focus light) decreases according to a curve represented by the shape of the light fans.

I agree with pmanson.
This pic has the advantage of being wider than that shown on Space Weather, and includes the pillars either side.

If they are vehicle or building window frame then the question must be asked - is this an artefact of frost or scratches on glass?

If from under a portico, with columns either side, no glass, then of course that doesn't apply.

John

Look a lot like the newfound (Nov2008) (yet to be officially named AFAIK) 'Riikonen arcs':

http://www.ursa.fi/blogit/ta/index.php?cat=67

Culprit would be a flattened hexagonal ice crystal.

--
jussi

Could it be a McDonald promotion gone bad?

As it is, each pillar looks like it has numerous rays emanating from the light source - some straight (in the bright centre) but also many curving and then crossing just below where they fan out.
The 'fanning out' looks like it's some sort of focussing issue. I this case the light sources are relatively large/wide light source, close up. In the case of sun pillars, the light source is relatively small, compared to the distance. In the case of the light pillars (http://antwrp.gsfc.nasa.gov/apod/ap060305.html), perhaps the lights in that case appear as a smaller/narrower light source, and thus not showing the fanning out (or it's occurring much higher up, and therefore not visible.)