Moving Ripples in a sundog

On March 26, 2017, I could observe this phenomenon for the second time. The first time I observed it in Munich about 20 years ago, when within a few minutes two boundles of “moving ripples” crossed a left-hand sundog. At that time I did not know what I was seeing. I learned it thereafter, also the name of the phenomenon, that it has been observed several times until then and that it may be related to acustic waves. Later, the video of the “extermination” of a sundog by a rocket launch became well known. But I did not see this phenomen again till March 26, 2017.

It is just a “must” for me to photograph with my pocket camera every halo I see mostly only to get the time mark of its beginning and/or end for the record. On that day I was several times on my balcony to check for halos. The sky had only contrail-cirrus (now officially termed Ci-homomutatus), but no halos. But once I discovered a faint sundog it may have been the only halo-active contrail-cirrus group of that day. I observed the sundog coming and going with the respective cirrus couds resp. the standing sundog against the moving clouds. The sundog was faint the whole time and all but remarcable. But then I surprisingly realized that there were some odd dark strokes crossing part of the sundog diagonally. Remembering the moving ripples, I immediately zoomed in. I could record this phenomenon in some pictures. It did last only about 30 seconds, but visually the dark stripes were much more evident than the photographs suggest.

The exceptionality of this observation was that the otherwise “moving” ripples were in fact “standing”: They moved with the cloud through the sundog. This can be seen very nicely on the photographs: the ripples seem to be a fixed structure of the cloud. But they were only visible in the area of the sundog. Outside this area the ripple pattern did not show up: the dark stripes were not there! Clearly recognizable is also the fact that each ripple began weak and increased its intensity towards a maximum in the centre of the ripple area, and to vanish at the other border of the ripple area.

Remarcable was also the fact that the ripples showed up only in a part of the cloud resp. the sundog area. For me it remains a mystery why (only) a small part of the cloud was “trapped” in these “acustic waves”…

Author: Christoph Gerber, Heidelberg (BW), Germany

Link to the topic: Collection of all known observations

Reflection subsun in Southern Finland

6th January, 2017, I observed quite a clear reflection subsun in the southern Finland.

It was morning,  local time around 11am. I looked outside and saw a nice sun pillar. And clouds, that were about to block the Sun. So I went to take photos of the pillar before it was too late.

I got the pictures and stayed for a while and saw the clouds running over the Sun. Surprisingly, the pillar didnt disappear. I waited for a little while longer but the halo was stubborn. Then I realized, the source was not the Sun, directly, but its reflection! The sea is a couple of miles away and wasnt yet frozen (map).

More pictures can be found here.


Author: Matti Helin, near Turku, Southwest Finland

Diamond dust halos in spotlight beam in the evening of December 2, 2015

45921_3bfac9da40b093f7ff4ab1552ac073a8Here are shown the rest of the photos from the night that yielded the second capture of the anomalous Wegener/Hastings. From the golf course parking lot, where we took those photos, we walked into the golf course, and were able to place the lamp even lower down.

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Another occurrence of anomalous Hastings/Wegener

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On the left anomalous Wegstings, on the right normal

In an earlier post we showed a photo of a weird downward curving patch of Wegener/Hastings. Here is another case that occurred 9 days later on December 2, 2015. This time we also got a nice comparison to normal “Wegstings” by superposing photos taken from the same camera position.

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Spotlight display with strong Moilanen arc (and a crystal sample)

45797_19c840d56e4e22e5729ed89c87cfe8dfAfter having been hunting diamond dust halos since darkfall, at 1 am we withdrew along with disappearing crystals back to aparment to sleep. But this did not mean calling it quits. The forecast was for the conditions getting better, so every one hour each of us woke up in their turn to check the situation.

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A major spotlight display with possible 4th Tape arc component

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On 23 November 2015, we were watching diamond dust halos develop under overcast skies in Rovaniemi. As we stood on a rectangular field a couple of hundred meters across, we followed halos slowly gather momentum in the spotlight beam, reaching climax when clouds were cleared away for a short while – and revealing at the same time also a lunar display. Here is an excerpt from Marko’s observation log written the next day:

“The display just adds gear. We are looking at beautiful subanthelic stuff, subanthelic arc, diffuse arc… It becomes monstrous when the cloud almost disappears. That is when we get also a moon display with full parhelic circle. No one seems to be in a rush to photograph the moon display. The beam display is sheer grotesquerity. The laser scapel sharp, 100% pure glitter of the tangent arc and uppervex Parry.”

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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

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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