I have written some thoughts on halo naming.
Google Docs:
https://docs.google.com/document/d/1wCHmYaO5bZHeeQH-uEhWV51xBj1i_oPDAtoWKbxrm0o/edit?usp=sharing
PDF:
https://drive.google.com/file/d/1X0pdvkEwQJFwNS6zBpOpWiVAnMTaFLkE/view?usp=sharing
Marko Riikonen
 |
| ©Marko Riikonen |
The Rovaniemi Display of November 11, 2023 – possibly one of the greatest and most bizarre Super Displays ever – a sentiment Marko and I both share. I was deeply fascinated by it when Marko first posted it.
https://www.taivaanvahti.fi/observations/show/119911
https://x.com/RiikonenMarko/status/1871867455959707898
Above are the original publication, along with additional photos and simulations uploaded by Marko at the end of 2024. In private correspondence with me, Marko mentioned that the identification of the 24d Column Arcs came from a suggestion by Nicolas Lefaudeux. The previous work of Nicolas and Marko has already addressed the simulation for most of the halos observed in this event.
However, previous simulations failed to match some halos in the photographs – for instance, the peculiar '35d Spot'. Some of the mysterious puzzles revealed in this event still require further exploration by halo experts and enthusiasts.
'35d Spot' is not at 35 degrees !
Ice crystals that produce 24d Column/Plate Arcs theoretically also produce 35d Column/Plate Arcs. But the problem is that the so-called '35d Spot' observed in this event does not align with the theoretical positions of 35d Column/Plate Arcs – it is clearly much closer to the light source.
Precise measurements show that the inner edge (closer side from the light source) of the '35d Spot' is about 32°, and the outer edge (farther side from the light source) is about 38°. Obviously, based on measurement result, they are not 35d Column/Plate/Parry Arcs. Some other types of halo must be present and is the main contributor to this strange bright paire of spots.
.gif)
I also tried exotic pyramid crystals (Miller indices: 3 0 -3 2, 1 0 -1 2, 2 0 -2 1, 2 0 -2 3, 3 0 -3 4, 2 0 -2 5, and 1 0 -1 3), but none provided the correct answer. Perhaps the approach using exotic pyramid crystals was wrong from the start, because even if some special crystals that haven't been found in atmospheric samples can form 32° radius halos, it would be difficult for us to ignore the other halos that would accompany them.
Despite many failures, I have recently found a better answer – The 22° Parhelia of the 22° Column Arc.
↓
The first record of '22° Parhelia of the 22° Column
Arc' ?
Multiple Scattering(MS) halos from 3-5 ray paths will be closer to the light source than 35d Column/Plate/Parry Arcs. However, differences in the order of 'the first/second type of crystals' can lead to different halo manifestations. I tested various combinations, and ultimately concluded that only the '22° Parhelia of the 22° Column Arc' provided the best match. The '22° Column Arcs of the 22° Parhelia' were ruled out due to unsatisfactory position and shape. MS halos related to the Parry arcs were eliminated because they were too sharp and also ill-positioned.
.gif)
The second scene taken by Marko also supports this conclusion. In this scene the camera pointed towards the zenith, and Marko had stacked the images, which is more conducive to revealing the ideal morphological characteristics of halos than a single image.
↓
.jpg)
Precise alignment work showed that the '22° Parhelia of the 22° Column Arc' once again performed very well. This time, even without the contribution of 35d Column Arcs, the '22° Parhelia of the 22° Column Arc' alone aligned the shape/position of the '35d spots' in the stack-image very well.
↓
%20%20Poster.jpg)
So, did Marko capture another Borlänge Arc?
No. I suggest that the situation in Rovaniemi on
Previously, on Taivaanvahti or TheHaloVault, the Borlänge Arcs were defined as a combination of both the '22° Parhelia of the 22° Column Arc' and '22° Column Arcs of the 22° Parhelia'. This conclusion is likely based on simlations in Halopoint. However, this might be incorrect.
https://www.taivaanvahti.fi/observations/show/79745
https://thehalovault.blogspot.com/2018/12/complex-halo-display-borlange-sweden.html
After using Zhang Jia Jie's program for further research, we can see the differences – the position and shape of the MS halos in Borlänge and Rovaniemi Displays are not the same. In the Borlänge Display, people likely only observed the '22° Column Arcs of the 22° Parhelia', with the '22° Parhelia of the 22° Column Arc' either not being a major contributor or not appearing at all.
A similar conclusion applies to the
Naapurinvaara Display in
https://www.taivaanvahti.fi/observations/show/95033
https://thehalovault.blogspot.com/2020/12/two-years-ago-halo-community-got-its.html?m=1
%20%20Gif.gif)
I'm unsure if there are other records of Borlänge Arcs around the world. The halo community can help verify this. If there has been no prior confirmed record of the '22° Parhelia of the 22° Column Arc', what Marko captured may very well be the first record of this phenomenon.
A proposal to redefine the
Borlänge arc
It was previously widely believed that both of the '22° Column Arcs of the 22° Parhelia' and the '22° Parhelia of the 22° Column Arc' should appear together, which if why the Borlänge Arcs were defined as a mixture of two halo phenomena. But now, should we consider the case of 'only one of them appears alone' – in such cases, they no longer fit the name 'Borlänge Arcs'. Jokingly speaking: a rock band typically has 3, 4 or 5 members; when one member appears alone, they cannot be fully equated with the entire band.
So, what should the new name be? Riikonen Arc? - that name has already been used for another halo. Perhaps Rovaniemi Arc is a name worth considering, or perhaps we should strictly name these MS halos according to their ray paths? In any case, Marko told me he has an article on halo nomenclature ready for publication, perhaps we will find better solutions for above discussions in his article.
A strange spot appeared on the inner side of the right 22° Parhelion. Obviously, it was not any odd radius halo.
To me, the reason for this phenomenon is the diffraction and interference of light. The USM images seems to support this speculation.
↓
These rare images were taken by ZHANG Jin Rong from the Chinese sky enthusiasts' community (in BeiJing, on January 1, 2026, from local time 15:50 to 15:56).
Several years ago, when the "multiple CZA" was discovered, it was also considered extremely rare. But nowadays, at least dozens of people around the world have captured the "multiple CZA". Perhaps, in the near future, more diffracted 22° parhelia will be recorded. Now I'm already looking forward to the discovery of the diffracted CHA. Anyway, what a crazy New Year gift for 2026!
