Crystal samples should be englightening, but all too often they just make you confused. The observation I made on 22 November 2015 in Rovaniemi is a case on point, although an observation recently published by Alexander Haußmann may now provide a solution.
During last year’s meeting of the German halo observers, we decided to drive on top of Mt. Klínovec (Keilberg) after dinner on Nov 27th, 2015. We used the car headlights as light sources for glittering diamond dust displays from ice crystals within the first few meters above the ground, while facing temperatures in the range of –5 °C to –6 °C at wind speeds of 5 – 6 bft. Simultaneously, there appeared a non-glittering, but slowly changing moon halo display in crystals higher up, including a “traditional” Moilanen arc:
(20:03 CET, unsharp masked, for the original image see here)
The mystery deepens. In two previous posts we wondered why some displays are great in their column orientation halos even though the crystals have well caved ends. Here we show a case that appeared on November 22, 2015 in Rovaniemi, where crystals seem not much different, yet rare halos requiring basal faces are completely absent. Even the 46° supralateral arc gives just a whiff. Poor crystal orientations can’t explain the absence of rare halos as the tanget arc is quite sharp. Had we known only about this display, we would be quite happy to explain with cavities, but knowing about the other displays, it is quite puzzling.
Marko Mikkilä, Jarmo Moilanen, Marko Riikonen
The four caleidoscopic arcs carry in their name the location on the celestial sphere where their loops’ cross. For three of these halos – helic arc, Tricker anthelic arc and subanthelic arc – there exists photos showing the crossing.
The diamond dust season is soon to arrive in Finland and it is time to wipe the dust off the equipment. In a meanwhile, here is the last winter’s starter for Rovaniemi, on October 30. The temperature during the display was -5° C, a quaranteed number for great stuff.
An impressive ice fog halo phenomenon occurred in Bremerhaven at Northern Germany’s North Sea coast on 21 January 2016. It lasted from the morning into the early afternoon. To observe such a halo display in Germany is quite rare by itself, but to have it in ice fog directly at the relatively mild coast is certainly exceptional.
Visually I was able to document the following types of halos:
• 22° halo
• Both parhelions (extremely bright at times)
• Upper and Lower tangent arc
• Upper and Lower sun pillar
• Circumzenithal arc
• 46° halo
• Parhelic circle (near the sun and up to 90° to the sun’s right)
• Supralateral arc
• Parry arc
• Tricker’s anthelic arc
Image processing revealed the following halos:
• Heliac arc
• Moilanen arc (without snow gun!)
More and more ski areas install webcams with a very good image quality. They doesn’t show only the current weather situation, but sometimes also halos. Most interesting are the webcams at the mountain peaks, which also show halo types below the horizon.
Such an interesting halophenomenon recorded the webcam Nassfeld-Hermagor in Carinthia, Austria on 3rd January 2016.
This timelapse shows all halos on that day.
Particularly interesting is the image of 2 ‘o clock pm. In addition to the beautiful combination of Infralateral and Supralateral arcs (right) the 120° subparhelion is also recognizable.
Such a halophenomenon had seen just a few of us in this characteristic.
Authors: Claudia Hinz, Kevin Förster, Andreas Möller
Here is divergent light subparhelia flanking the pillar. Spotlight displays are classical displays with little divergenness involved. A way to create truly divergent halos with spotlight is to point it to the ground. The reflection from snow then acts as a divergent light source. Another way that might work is to cover the lamp glass with a layer of snow. That would be a shorter lasting solution, though, as the heat of the lamp will melt the snow.
Most spotlight halos are visibly formed of separate crystal glitter. Not the divergent parhelia. They are solid objects floating majestetically in the air. One feels humbled before their lofty heights, just as a lesser subject might feel in the presence of royalty.
Below is another photo of divergent subparhelia taken some hours later. And also a little lunar display from the same night, which was the 18/19 January night in Rovaniemi.
Jarmo Moilanen / Marko Riikonen
Nothing out of the ordinary here. Just a plate display and its crystals. Visible are the usual folks: subcza, sub-Kern, sub-120° parhelion. The behaviour of the last one in spotlight displays is a little curious, though: while it comes out well in photos, visually it is cryptic. One has to run along the beam to see that ghostly spot of sub-120°. It is not made of big glitter like the sub-Liljequist parhelia – it does not seem to be made of much glitter at all, just faint diffuse spot of light.
Rovaniemi, in the morning hours of 19th January .
Jarmo Moilanen / Marko Riikonen
It is difficult to get a matching simulation of pretty much any spotlight display. Some details tend to be always wrong. But one can usually obtain what could be called an acceptable approximation of the real thing.
The shown display is a true rebel in this respect, for it comes with three anomalies too blatant to be swept under the rug. First, the subparhelia were brighter than parhelia (this we noticed also visually). Second, of the Schulthess arcs (the arcs from Lowitz orientation) only the concave component was visible. And third, there is no subparhelic circle opposite to the lamp.
We can not simulate any of these anomalies. The solitary presence of the Schulthess arc concave component is not a new thing, there exists a handful of such displays. The missing of subparhelic circle opposite to the lamp in this level of display is something unheard of, as is the inverted relative brightness of parhelia and subparhelia. In the simulation above (light source elevation -5 degrees) only plate oriented crystals were used. Below is a sample of the simulation crystal shape variation, the “mother shape” shown in the upper corner.
The display had also a weak segment of parhelic circle between subparhelia. The crystal shape shown above struck the right balance between the sub-Kern and the parhelic circle segment inside subparhelia.
The night was 18/19 January, the location the Sieriaapa bog in Rovaniemi. The temperature was – 29° C.
Jarmo Moilanen / Marko Riikonen