diamond dust halos

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An occurrence of anomalous Hastings/Wegener

45820_e662e364876303651b6b4fbc10d66a83The image above shows what looks like a patch of Wegener or Hastings on top of the 22° halo. But instead of having the usual horizontal curvature, it is bending slightly downwards. Because of the view angle, though, the effect is not as evident as it could be. Anyway, if it were standard Hastings or Wegener, it would curve steeper up in the photo.

We have no idea how it formed, our attempts at simulating have come up empty-handed. The display was seen in Rovaniemi on 23 November, 2015, and the arc appeared at a stage when the display was still progressing to reach its peak.

Nine days later, in the beginning of December, we got another, better sighting, suggesting it is not exceedingly rare. In a similar manner, it did not occur when the display was at its best, but when the display was undergoing a momentary low. We will post about this later.

Jarmo Moilanen, Marko Mikkilä, Marko Riikonen

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Segments of a circular halo from Moilanen crystals observed Nov 27th, 2015, on Mt. Klínovec (CZ)

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:

2015_11_27_2003_30s_imgp3912_usm(20:03 CET, unsharp masked, for the original image see here)

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All rare halos are missing in this spotlight display, but why?

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

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Solar diamond dust display with 87° arc

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A stack of 40 photos. An average stack has been combined with maximum stack to show the crystal glitter of the 87° arc. The photos were taken during ~2 minutes. Sun movement has not been accounted for.

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.

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Ice Fog Halo Phenomenon in Bremerhaven at the North Sea

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!)

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Webcam Halos in the last winter season I

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.

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1400usmThe lower part of the Wegener anthelic arc is here faint visible. But even better it is seen at the 3 ‘o clock pm image, furthermore heliac arc and subparhelic circle.

1500

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Such a halophenomenon had seen just a few of us in this characteristic.

Authors: Claudia Hinz, Kevin Förster, Andreas Möller

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Making divergent subparhelia with spotlight

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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

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The hiding sub-120° parhelion

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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

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