Tuesday, 10 October 2017

Halos on 6th March 2017 in Rovaniemi

This display came into existence suddenly, when in the morning sun came out from behind a clear cut edge of a receding cloud area. Some points:

- Ounasvaara arc in a solar display
- There is a kind of extension to the Ounasvaara arc which makes it drop shaped. The extension is responsible for the narrow end of the drop near the helic arc. It seems to be present also in the first Ounasvaara arc display. It's caused by the same raypaths as Ounasvaara arc, but with an added basal face reflection.
- 120° arcs. Simulations say they are formed in Lowitz oriented crystals. The halo is not centered on 120° parhelia: it lies along a circle of 60 degree radius centered on the subanthelic point. It is made by raypaths that in plate oriented crystals give 120° parhelia and sub-120° parhelia.
- An uppervex Hastings in solar display. All the others the spotlight ones are indirect detections, because the lamp has always been at an elevation where Wegener and Hastings overlap.
- Helic arc is brighter than subanthelic arc. I could simulate this by lengthening the Parry crystals, but then the simulation went wrong in other ways too much. If we can't get this right, it kinda tells me we don't understand this display. I was told that I probably regret of not taking a crystal sample. It had not occurred to me, but once I was reminded, it was obvious that I should. In the simulation no column shaped crystals were used. It would have been of interest to see whether the crystal sample concurred.

This version was worked by Nicolas Lefaudeux
I also regret of photographing this with Nikon D3200 which is why we have to suffer all the artefacts. Not that there would have been any choice at the time, but about a month earlier I was offered a chance to borrow D800 for my halo hunts. I declined in fear of breaking it. A third regret, that was more personal and could have been easily avoided, was that I didn't have mirror with me and thus did not see many things. Didn't see, for example, the 120° arcs, Hastings / Wegener separation, both of which would have been visible easily with mirror. Spotting the 120° arcs in situ  that would have been something. 

The display occurred at around -17° C. You don't expect a major display at such temps in Finland. But sometimes they do occur, like was the case with Mikkilä's Kern display in 2007. Low supersaturations were in my mind the key here. They were low because the night was cloudy and thus the diamond dust could not have spawned before the morning when it started clearing up. And at that point, with the sun above horizon at such late time in the season, the air was not getting so much colder as for supersaturations to increase to the point of crapping the display (which is the usual scenario).

This post was modified on 15 Oct 2017 to replace the simulation with a new one. It has labels added to mark some of the features that seem to appear in the photos (sorry for the degree numbers having placed at the end of halo names, there is some glitch in Photoshop which forces this). Also, the parameter file was replaced becase I adjusted the parameters of the column oriented population a bit, increasing crystal h/d from 0.5 to 0.8 and making it a little more triangular. This more burned more fine grained simulation has gained features that are not seen in the images. Possibly with a better camera some of these could have been dug out from the display. 

The post was further modified on 21. Oct by adding "originals" of the stacks.


A singe frame from the very beginning of the series (added 11 Oct. 2017)
"Originals" of the stacks.


  1. This is arguably the finest display that has ever been photographed. Rovaniemi 6th March 2017 will go down in halo history and will be the benchmark against which all other displays will be measured.
    The number of new halos that Marko has discovered is incredible;his work and sheer committment needs to be officially recognised by the wider scientific community. He certainly deserves the best equipment to continue his work.

  2. Great! We can stop speculating on what Biese and others actually saw in the Kuusankoski display, as here are the photos.

    Are these stacks or single frames and how long did the show last? Were you the only witness in the whole of the Rovaniemi metropolitan area?

  3. I can't believe what I am seeing!!! It looks like halos I have simulated with halosim!! I never dreamed they would be photographed!!! This like a dream. This makes the south pole display of 1999 look wimpy.

  4. These are stacks. The first one has 46 frames taken in 3m54s. The second one I am not sure. That view has 74 frames taken during 6m29s, but I don't think I used them all because the display was weakening. Normally I put in the file name the frame numbers, but this time I had not done it.

    I added at the end of the post a single frame from the very beginning. So it was not quite that magnificent display.

    The swarm was narrow. Just a few hundred meters I would say. It trailed east along the northern flank of the elongated Ounasvaara hill (the most common diamond dust scenario in Rovaniemi) and was over areas where there are no roads. Only 6km away from the guns there is a road which would have cut its path, but there was nothing - the swarm did not reach that far. I went there to reconnoiter when the sun was still behind the cloud.

    I ended up at the golf course pond where it looked like I was right under the swarm. I have seen many a good display there before. This location is about a kilometer from the ski jumps where the guns were running, making snow deposit for the next season. There was another person where I was, a guy practising golf. They had made with slope machines a little winter golf course around that area, complete with smoother "greens", holes and flags marking them. I shouted the guy to look up and he did, but continued concentrating the on the golf ball. However, next time I saw him he had forgotten about golf and was taking photos of the display with his cell phone. He became really animated actually, scuttling around and taking photos from this and that spot. The photos must have went online somewhere. I don't think many other could have seen this. The swarm most likely did not extend over any roads that could be reached with cars.

  5. Marko, you've written halo history. Again. I'm at work now, but have to get back to this post every now and then to marvel at it.

  6. Hey Marko, I hope you do more displays where the spotlight is under you and hope you get a sub-CHA

  7. Not doing this winter. I have moved out from Rovaniemi. Around here in Joensuu there are chances too, but it is nothing like in Rovaniemi. Conditions occur much less often, places to photograph are not nearly as abundant, and there are no chances for "under the brige" stuff. Rovaniemi spoils you - after two winters there I feel like it is not worth doing spotlight elsewhere. But there is also the equipment issue. If I return, I'll do that only once I have gear that is up the task.

  8. Multitudes of reasons. For one thing, I have been staying in Joensuu already since spring and started rooting here. But returning to Rovaniemi is not out of question.

  9. I hope you visit Rovaniemi for the super halos I want to see more of your super halos and try for some nice superparhelia

  10. Yeah, superparhelia is really something. I saw a couple of cases of most awesommest superparhelia last winter from the side of the beam. I just stared at them with jaws open. It is possibly the most maginificent effect you can see with spotlight. But you gotta see it with you eyes, photos do no justise for it.

  11. Hi Marko,

    congratulations to this outstanding display with strong Parry and Lowitz species! Great to see the Ounasvaara arc made by sunlight, even in the single frame. The Schulthess arcs are also very impressive.

    Maybe a silly question: Were there ordinary 22° parhelia or distinct 120° in the display? This is not clearly visible from the processed photographs. I'm wondering if there was a classical plate oriented population involved at all. Perhaps there were only Lowitz plates?

    Sorry for the late answer, but university still keeps me pretty busy these days.

    Best regards,
    Alexander Haussmann

  12. There was normal parhelia, they just got overexposed in afterprocessing as I tried to maximize the visibility of the less bright halos. I'll add in the post later another image that shows the parhelia. Anyway, the cza should tell about normal plate population.

    Yeah, the S arcs are impressive (I am not satisfied with the name, so I avoid using it). By the way, and interestingly: last winter there was in Rovaniemi a display that looked pretty identical to this one, just fainter:


    Eresmaa asked how long the display lasted. In one of my comments above there is alreaydy an indication that it did not last long, but let's be more specific. The first photo was taken at 8:11. But the display had been in existence for some 5 or a litte more minutes by then. I missed the beginning because I had walked to the pond to wait for sun's coming out from behind the cloud without camera. The expectation was it would be the usual crap as temperatures were in the most crappy numbers. So when suddenly there was this display I had to run to car to get camera, tripod and blocker. The display was weakening pretty much constantly because of the sun's heat killing the crystals. The last photo was taken at 8:36, when there was not much left.

    So, I still keep thinking that Kuusankoski was in high clouds. It occurred over hundred or so kilometers of area (from near Tampere to Kotka), for one thing.

  13. Marko, I hope you can go out this winter and find some more super halos

  14. Just as a side note, the CZA surely hints at plates, but it can also result exclusively from Parry crystals (and should in such a case be counted as a member of the Tape arc family). That's why 22° or 120° parhelia would be the only unambigous evidence for a plate population (ordinary, not Lowitz ones). But anyway, the great stuff is made by the Parry and Lowitz crystals here.

    Alex Haussmann

  15. You are right, Alexander. I didn't think about cza being made also by Parry crystals.

    And there is no 120° parhelion visible in the sideview photo, something that I have been wondering about. In the image the area is whited out, though. Gotta add that less worked image soon to the post.

  16. I suppose that diamond dust displays are possibly one of the only exceptions where using a halocam would not be desirable. We speak of "hunting" in relation to these displays because the swarm is in constant motion, almost alive, almost with a will of its own. This is why an observer on the ground with transport and armed with the necessary equipment, prepared to move location at a moment's notice will always be required. That being said, I also think that new and improved automated halocams are the way to go for most other displays. I can guarantee that many other halo forms will be discovered in this way over the coming decade.

  17. Less worked versions of the stacks added to the end of the post. There is no 120° parhelion. But it may be hidden behind that tree not far away from the camera. Without the tree, the 120° parhelion core would probably be located against the more distant forest. The parhelic circle is visible against the forest, so we can speculate that 120° parhelion may have been visible too.

  18. Hope you can get some super halos this winter