Two diamond dust displays in Finland

Miika Karppinen photographed this display in the town of Kajaani on 8 March this year. Upper sunvex Parry arc and 46° Parry arc are weakly present ( 1 ).

The other display occurred on 26 October 2006 in Salla ( 2 ). Photos were taken by Jani Päiväniemi. Under the circumzenith arc there is a patch of 46° halo, which could be indication of 46° contact arc. First convincing photos 46° contact arcs were taken three days later in Muonio ( 3 ).

Both Kajaani and Salla displays were captured with cell phone cameras.

Wegener Arcs in Finland

Long absence of rare high cloud halos in Tampere skies was brought to a sudden end by a complex display on 2 May 2008. Singly and Parry oriented columns played the key roles: among the more common halo forms the display featured an upper suncave Parry arc and Wegener arcs.

Sun elevation was ca. 27 degrees. Both photos are stacked images (no longer than 5 minutes' time period for each). Below them contrast enhanced versions are provided. Also, larger images are available online ( 1 ).

Complex displays in Eastern Europe

A series of complex halo displays occured in Eastern Europe between 27 March and 6 April. The first display was seen in Vecsés, Hungary (observer: Ágnes Kiricsi). On 27 March, after the appearance of a bright circumscribed halo, a growing stretch of the parhelic circle came to sight ( 1 ) and 120° parhelion showed up on the left ( 2 ). The parhelic circle was complete for about 5 minutes.

Close by in Budapest, a Tape arc was observed in the evening. Images were taken by Alexandra Farkas and Tibor Hollósy ( 3 and enhanced 4 ). They did not see other halos formed by Parry oriented crystals, but 7 km to the north of them and only 3 minutes earlier, Márk Laczkó had photographed an upper suncave Parry arc ( 5 - 6 ).

The next Hungarian observations of complex displays with complete or almost complete parhelic circles were on 1 April (Ágnes Kiricsi in Vecsés) and on 5 April (Alexandra Farkas, Tibor Hollósy in "Remete" Gorge).

On 2 April, Marko Krusel had an opportunity to observe a complex halo display in Estonia, nearby Keila (see image on top). Besides all the common halos, he got an upper suncave Parry arc, a full parhelic circle and 120° parhelia. A fragment of the infralateral arc was seen on left. The show ended with the parhelic circle and 120° parhelion as the latest leavers ( 7 ).

6 April was a favourable day for the Czech Republic and Poland. The Czech Matej Grek (Ostrava-Dubina) and Martin Popek (Nydek) both photographed complex displays with parhelic circles and bright circumscribed halos. A 46° halo was also visible ( 8 - 9 ). In southern Poland Jakub Marchewka observed a display with full parhelic circle in Chrzanów ( 10 - 11 ). From the photos he noticed a faint Wegener arc ( 12 and enhanced 13 ) and 46° halo ( 14 and enhanced 15 ).

It was a first observation of Wegener in Poland and one of the first of 46° halos. The latter was described by Johannes Hevelius on 20th February 1661 in Gdańsk, but it is likely that supralateral and infralateral arcs were the main contributors to the phenomenon.

Text: Marko Krusel, Jakub Marchewka and Ágnes Kiricsi

Subsuns from space

The publication of the Mars halo on this site stimulates me to dig in history. On 27 April 1975, I saw by change a picture of a subsun taken from space ( 1 ). It is here on the frontal system on the right of Greenland. It was taken by the satellite ESSA 8, which was the last weather satellite that took real pictures of the Earth rather than being a scanning platform. Only a few months later, ESSA 8 was lost, so I had been very lucky. The discovery of the subsun on a satellite picture gave me the same sensation as the discovery of the subsun on Mars, 31 years later.

In 1985, I got another subsun taken from space (see photo on top), taken by the Dutch astronaut Ockels from the Challenger space shuttle during its last flight before the crash. The subsun is visible over the Netherlands, viewed upside down. Interestingly, the astronaut had overlooked the subsun despite the fact that I had prepared him for this possibility. He only saw the thing when he gave a slide show and I put his attention to it. Note its white colour compared to the sun’s reflection in the sea. Contrary to the ESSA 8 subsun on which I wrote a short paper in Weather, I did not publish this one.

Text: Günther Können

An unknown halo and other displays by Jukka Ruoskanen

Jukka Ruoskanen has scanned his best halo slides ( 1 ). The material spans from year 1988 to 2005 and includes several displays of interest. Some cases are rather puzzling, like the one shown above, photographed on 23 December 2001. It contains strange pillars next to sun pillar. Explanation for these arcs is not known.

A halo on Mars and other papers by Gunther Können

Gunther Können, who has produced a decent number of halo papers, has put his works on-line. These are found in the atmospheric optics section of his web page ( 1 ). Among others, there is an article about subsun on Mars (right photo), as photographed in 2006 by Mars Global Surveyor (left photo). Also, the extensive work on halo systematics, "A general setting for halo theory" by Tape and Können, is available.

Image credits:
left - NASA/JPL-Caltech/Corby Waste
right - NASA/JPL/Malin Space Science Systems

Subsun and Bottlinger's ring

Dmitry Savvateev observed a subsun in 2006 in the Khibiny Mountains (Kola Peninsula, part of the Murmansk region). This subsun, however, seems to be accompanied by a much rarer halo: Bottlinger’s ring. Even though this case is a marginal one, the elliptical halo appearing around subsuns is so infrequent that the photo is worth showing here ( 1 ).

Just as elliptical halos formed around the Sun, Bottlinger’s rings can also be of one, two or three ellipses. The 1997 photo taken by Frank Wächter shows multiple rings ( 2 ), in the Khibiny picture, there is only one ellipse.

Display in Yuzhno-Sakhalinsk

Dmitry Kuznetsov saw this complex display in Yuzhno-Sakhalinsk on 1 April 2007.
The vertical arrows in the photo denote the Wegener arc and the horizontal arrows point at faint helic arc. Dimitry described also subanthelic arc, but it is located outside the photo. More photos are also available ( 1 ).

Halo vs glory

The photo above is intended to be food for thought, as it shows a rather controversial phenomenon.

Mónika Bodó took this picture on 27 March 2008 between 16:43 – 16:46 on a flight from Athens to Budapest. As an air hostess, she flies several times a week, and very often photographs subhorizon halos and glories. This was the first time, however, when she saw such a phenomenon. For comparision, the original version of the above photo ( 1 ) and another image are also available ( 2 - 3 ).

The bright spot in the picture is at the antisolar point, the location of both the glory and the "subanthelion". A short time earlier, the shadow of the airplane had been photographed ( 4 ) and it was exactly at this point where the brightening developped. On the other side of the airplane, the bottom of the 22° halo, subsun and subparhelia were visible ( 5 – 6 ).

When the "subanthelion" is photographed, it tends to appear where the diffuse anthelic arcs forming a large X cross the subparhelic circle, and the brightening seems to be caused by the meeting of these halos. On 7 August 2006, Francesco De Comité took a photo of these antisolar halos, and there the shape of the "subanthelion" is clearly a square, thus suggesting that it is not a separate halo form, just a bright spot created by the crossing anthelic arcs ( 7 ). Another image was taken by Susanne Danßmann on 3 June 2006 ( 8 ), and one can be seen in Walt Tape's Atmospheric Halos (page 71).

What makes Mónika Bodó's observation very interesting is that even though the spot looks like a halo, the subparhelic circle does not show up in the images, and there are no other halos visible in the antisolar region. If it is really a halo, her photograph seems to show one not caused by the crossing of these arcs.

There have been other observations of a single bright spot at the antisolar point, often taken as a distant glory. It might be, however, that it is indeed an independent halo form. So far no sufficient explanation exists, suggestions and opinions are welcome.

Two hour long elliptical halo display on 23 March

While working on a wood bowl in my workshop I noticed a lot of Altocumulus clouds that were turning into ice crystals. That meant a chance of elliptical halos. I took my camera, went for a walk, looked up and there actually was an elliptical halo! I ran like mad to get a macro lens and then used a telephone pole to shield the sun while shooting.

After about 10 minutes the halo was gone but I kept a vigil on the sky. Patience was eventually paid off as more dissipating Ac cloud moved in and the display came back.

I later positioned a large wood stick with lens case to block the sun and laid on my back and watched the show. The magic really began when a large Ac fragment passed in front of the sun and turned into ice crystals. It showed three elliptical halos at once, sharp and bright and they were colored like the classical halos ( 1 - 2 - 3 ).

The display lasted for two hours. One thing I noticed while laying on my back and taking photos was that the ellipse would start out large and then gradually shrink.

46° halo on snow surface in Juva

On 22nd March Jari Piikki photographed a 46° halo on snow surface. He took 20 photos and stacked them to come up with a photo above. The sky is from a single frame.

Two halo days in the northern part of the Czech Republic

At the weekend of 15 – 16 March, observers in the northern part of the Czech Republic had some opportunity to see rare halo phenomena. On 15 March, in the afternoon, fine cirrostratus came from the west, and subsequently bright halos appeared.

Patrik Trncak took a series of photos of the display. The most uncommon halos that he observed were the Wegener arc, which crossed the parhelic circle; and the Tricker arc, which was noticed afterwards on the images processed by Registax ( 1 ).

The next day, the situation was similar, but the Wegener arc was brighter and the cirrostratus clouds lasted for a shorter period ( 2 ).

I (Martin Popek) didn’t have such good luck but I could also observe some interesting halos. On the first day, a nice suncave Parry arc was visible, which shows well on the stacked images. By the bright parhelia, Lowitz arcs appeared, and after a long period of time I saw an infralateral arc, as well ( 3 - 4 ).

On the second day, the halos were less numerous. There was only one that is not so frequent: a faint 46° halo ( 5 ). Later I observed an interesting lunar display, too, including a diffuse 9° halo ( 6 - 7 ).

Text: Martin Popek, Lukas Shrbeny

22° halo on snow surface

Sirkka Sario took this photo in Lake Jerisjärvi, Muonio, on 5 March. Another photo is also provided ( 1 ).

Name change

Although our blog name "Halo Reports" had served reasonably well all these years, we felt it is time for a change. The blog is now "Ice Crystal Halos". The new name goes straight to the core of the things and is self explaining enough so that the subtitle was not necessary anymore.

New address for the blog is http://www.ursa.fi/blogit/ice_crystal_halos/index.php
The old address works as well. Veikko Mäkelä mastered the change so that links to photos in blog folders were updated accordingly.

Hope you feel ok with the change.

Distinction of 22, 23 and 24° halos from snow surface

A broad 22° halo is observed in most odd radius displays. One factor explaining the broadness can be simultaneous occurrence of 22, 23 and 24° halos, or any combination of two of these halos. As we know, separation between 22° and 24° halos is detectable, but 23° halo has not been distinguished from the other two so far.

In the image above all the three halos are separated. This was made possible - in addition to having a suitable display - by stacking an extensive amount of images of a snow surface display. Using Rexistax, total of 379 frames were stacked and the resulting image was further stacked with its mirror image, essientially doubling the frames used. The separation of the three halos is seen also in non-mirrored image ( 1 ).

9, 18, 20, 35 and 46° halos were present as well. The first three are visible in the above image, which is a close up of 8 mm fisheye image. The 9° halo, of which only the lowermost part is seen, is overexposed. An image with only minor digital enhancement is given for comparison ( 2 ).

Three versions of full frame image show the 35 and 46° halos ( 3 ). A single frame ( 4 ) reveals the true nature of the display: it was nothing a passer-by would notice, and to me it might not have been any special unless I had known that day earlier in the same place odd radius halos were observed ( 5 ).

The photography was done on river ice in Rovaniemi in February. The method was to take 3 to 5 photos from different heights by adjusting vertically the tripod central bar and then moving the tripod some 20-30 cm and again taking a set of photos, and so on. This was faster way to obtain large number of photos from different positions than moving the tripod after each shot, as was done day earlier.

Samples of snow surface crystals were photographed in the location as darkness was approaching. Pyramidal faces were abundant ( 6 - 7 - 8 - 9 - 10 - 11 - 12 - 13 - 14 - 15 - 16 ).

The issue of pyramid crystal formation temperature was addressed in the discussion of the previous day display. Again the temperatures were not that cold, previous night was around -10 °C and it was cloudy. It cleared up in the morning and minimum temperature in the official measuring point of Rovaniemi center was -12 °C during the photography soon after midday.

It may be that snow surface presents a special situation concerning the pyramid crystal formation (and maintenance) temperatures. There is some evidence in the literature that pyramid crystals can exist on snow surface even at as high temperatures as -2.5 °C.

Whether that is really the case, it is nevertheless good to keep in mind that odd radius halos may exist on snow surface in “unconventional” temperatures and they may be much more common than we have known. However, these displays may not be easily recognized as special and stacking might be needed to visualize them.

Two diamond dust displays near Moscow

On 21 February ice crystals filled the air in Rumyancevo, a suburb of Moscow, and a halo display with relatively strong Moilanen arc was photographed by Alexandr Yakovlev. One of the photos, with unsharp mask enhancement, is shown above. Another photo is also given ( 1 ).

A year earlier, on 1 February 2007 Yakovlev photographed a diamond dust display with subsun and subparhelia from the 7th floor of a building ( 2 - 3 ). In the photos Moilanen arc is also present faintly. An unsharp masked image shows it better ( 4 ).

The original images of both displays are available on my blog ( 5 ).

Diamond dust display in Dolni Morava

On 29 December 2007, Radomir Vondra observed a complex diamond dust display above an inversion cloud layer. He was walking to the ski slope in the village of Dolni Morava, when he saw the halos between 12:30 and 13:00. The elevation of the Sun was about 15 degrees above the horizon, and the dominant phenomena that first appeared were the parhelia and a bright circumzenith arc. Later, after the sky got clearer, a suncave Parry arc appeared above the upper tangent arc. An unsharp masked version of the photo is also available ( 1 ).

On the same day, Matej Lebl observed well-defined parhelia in Rokytnice nad Jizerou ( 2 – 3 ).

Text: Martin Popek, Lukas Shrbeny

ESEM column crystal photo

Column crystals are a dime a dozen, but the ones shown here are nicely positioned and thus unusually revealing. Although we were collecting atmospheric crystals at the time, these monsters are probably frost crystals from the dewar mouth that fell into the liquid nitrogen and contaminated the sample. The photo is by Tom Kircher at the Advanced Instrumentation Lab, University of Alaska.

Text: Walt Tape

Moilanen arc in Zaton, Sumava mountains

On 3 February, Milan Osecky observed a diamond dust display with sharp Moilanen arc by the village of Zaton. The halo was seen during sunrise, when the Sun was about 4° above the horizon. The phenomenon lasted approximately 8-10 minutes, starting at 8:05 and disappearing completely by 8:15. Also a diffuse sunvex Parry arc was observed, which was a bit difficult to distinguish from the upper tangent arc due to the fuzzy border between these two arcs.

On the same day, Martin Nekola saw halos on mount Svorova in the Krkonose mountains. The photos show 22° halo, parhelia, pillars, upper tangent and infralateral arc ( 1 – 2 ).

Similarly, Tomas Trzicky in Jizerske hory observed well-defined pillars and upper tangent arcs in the light of street lamps ( 3 ).

Text: Martin Popek, Lukas Shrbeny

Reflection subsun in California

On 1 February, Steve Sumner in Auburn, California, observed a peculiar phenomenon in the sky. A bright elongated spot, which was apparently not lit directly by sun rays, occurred in front of an Altocumulus cloud. In the photo the Sun's rays projecting downwards from small openings in the cloud layer reveal that the Sun is positioned behind the cloud at the same location as the spot. The other photo of the display should stand here, as well, for comparision ( 1 ).

This phenomenon is the reflection subsun, a rare halo of which only two previous documentations are known. Its formation involves two reflections from horizontal surfaces: the Sun rays are first reflected on a body of water, and then again on plate crystals in the sky, which precipitate from the Ac cloud that blocks the Sun. This way the reflection subsun is seen just where the Sun should be.

Identifying the reflective surface was not obvious in the beginning for Sumner. "I could not figure out for a long time where the body of water might be that would reflect the sun in such a way that the halo could appear," he wrote. Then he remembered a place called Yolo Bypass, a large area to the west of the obsering site that is designed to flood during the winter and spring. "Due to the heavy rains we have experienced over the last several weeks, the bypass has been filled with water, and that must be the source of the required reflective surface," Sumner said.

In the map linked, the green arrow marks the point of observation, the yellow line starting there shows the Sun's direction, and the large blue area that it intersects is the Yolo Bypass ( 2 ).

Knowing that the Sun was at 6.5° elevation during the observation, and assuming that the Yolo Bypass at 56 km from the observing site was the primary source of light for the reflection subsun, Sumner calculated that the ice crystals were at about 3500 meter elevation, which is an agreeable value for Ac clouds.

Sumner’s photograph adds the third documented case of reflection subsun. Earlier, in Finland, Jarkko Korhonen had photographed such a halo in Oulu in October 1998, and then Jenni Elina Holopainen on 18 May 2006 in Pyytivaara ( 3 ).

Stacking an odd radius display on snow surface

For some years I have been waiting to get to employ stacking technique for snow surface halos. Last weekend the chance finally came along, as a moderate display appeared on two consecutive days. Here I present the results from the first day.

The image above is stacked from 118 images which were taken on a frozen river in Rovaniemi. Between each shot the camera, which was on tripod, was moved some 20-30 cm sideways. This serves to decrease noise of the snow surface in a similar manner as cloud movement decreases the noise in stacking of sky halos.

Already on the spot I thought of seeing double structure in 22° halo, indicative of the 24° halo, but was not certain of that until two hours later, when I came back with microscope and saw an abundance of pyramid crystals among normal crystals in samples taken from snow surface ( 1 - 2 - 3 - 4 - 5 - 6 - 7 ). In the above displayd stacked image the 24° halo is conspicious and also a close up image is given ( 8 ). 24° halo is seen also weakly in single unmanipulated images ( 9 ).


9° halo, which should be always occurring with 24° halo, is not visible in single images, but appeared in stacked image, and is seen perhaps best in an image that has only light unsharp masking ( 10 ). Heavily unsharp masked version resulted in 35° halo appearing faintly ( 11 ). At 86 frame stage I could not yet detect it, so additional 32 images made a difference.

In sky displays 35° halo is always associated with 20° halo because they are closely related in formation. As a thumb rule, one can have 35° halo if 20° halo is intense enough.

Here, however, it seems that there is no 20° halo or at most a ghost of it is present. Possibly the alternate pyramid faces, which make the 35° halo, are represented in the special snow surface situation in significantly greater proportion in relation to opposite pyramid faces, which make the 20° halo.

The lowest temperature measured at the official station in the city center was -12°C at 9 in the morning, three hours before I noticed the phenomenon. This is not quite enough for pyramid crystal formation as far as airborne crystals are conserned, which start occuring below -20°C.

However, down on the river ice away from the city center and especially on the few centimeters above the snow surface (clear sky) it can have been cold enough for pyramid crystal formation. Could be also that snow surface presents a special situation where not as low temperatures are required as with airborne crystals.

The crystal photos are all in same scale, the width of each square is approximately 0.6 mm.

The next day the display looked slightly different but pyramid crystals and odd radius halos were still present. I took 350 photos but have not worked on them yet.

Snowgun jewel from two years back

The morning of 16th March 2006 offered a perfect ending for skiing holiday week for Hinkka family, when a magnificent diamond dust halo display interrupted their outdoor activities near Himos ski resort. Markku Hinkka drew camera out and started shooting the sight. According to his story at least a 120° parhelion along with bunch of other halos was in the sky. However, he did not photograph these due to their less appealing appearence compared to the halos in the vicinity of the Sun.

Markku describes the weather being windless and "very foggy". The temperature was around -10°C. The snowguns were in operation and the halo was visible at least from a distance of 150 m up to 1,5 km from them.

The accompanying image is a collage of several individual photos taken by Markku Hinkka. In the process of making the collage the perspectives of some original photos have been twisted in a very violent manner. In this case the purely illustrative purposes justified the manipulative actions, but if any measurements or comparisons with simulations are intended, such twistings are highly inappropriate. The writer takes full responsibility for these twists.

Snow surface display with 9° and 24° halos

Sometimes a surface halo can be more than a couple of colored crystals forming a vague half circle on the snow. Such was the case on 8 January 2006 in Juva, where Jari Piikki photographed the display shown above.

22° halo is the dominating feature, but closer look reveal also halos from pyramid crystals. In darker version of the same image 9° halo is visible and a short patch of 24° halo is seen on the right where the 22° halo meets the forest ( 1 ).


Earlier, an odd radius halo had been observed on snow surface in Germany, where Richard Löwenherz saw 24° halo accompanying the 22° halo on 10 December 1998 ( 1 ). On 3 December 1986 in Kuopio, Finland, Juhana Hakumäki observed 9° and 22° halos on frosty window. The 22° halo was reported to have double spectrum, an indication of the presence of 24° halo.

Crystal photos from surface halo displays are scarce and as far as I know none are available from the displays with odd radius halos. However, pyramid crystals have been sampled from snow surface. At South Pole in December 1998 Jarmo Moilanen decided to have a look at the snow surface composition under a microscope, and to his surprise saw pyramid crystals ( 1 - 2 ). Unfortunately sun was too high to see the possible odd radius halos.

Sunvex Parry arc on Lysa hora

In the evening of December 22, 2007 Emil Brezina had the opportunity to observe halos on cirrostratus clouds from the top of Lysa hora, the highest peak (1323 m) of the Moravian Beskydy mountains.

Among these halos, there was an expressive sunvex Parry arc, which can compete in brightness with diamont dust halos. The development of the Parry arc and upper tangent arc was photographed between 3:17 and 3:34 pm, and further photos of the display are also available. ( 1 - 2 - 3 )

By chance I (Martin Popek) observed the same sunvex Parry arc about 20 km from Lysa hora but the quality of the photos cannot be compared. ( 1 )

Text: Martin Popek, Lukas Shrbeny

Odd radius diamond dust from Fairbanks

A one night cold snap in Fairbanks on 24 January produced the above display with halos from pyramid crystals. Let Walt Tape, who took the photo, tell more:

"The temperature was between -25 and -30 °F (-32 and -34 °C). The crystals were probably power plant products, but I am not absolutely certain of that; there was a gap in the crystal swarm that occurred between the main plume and the area of the display. I did not see the 9° or 24° arcs in the spotlight. The photo was taken on the main highway between Fairbanks and Anchorage, which was not getting heavy traffic at 5am".

Two more photos ( 1 - 2 ).

Kern arc in searchlight beam in Kilpisjärvi

Sometimes it happens that when first photos of some halo are taken, more start piling up in the wake. This was the case for example with elliptical halos.

Now the Kilpisjärvi halo expedition seems to have resulted in second Kern photo, this time the light source being Cyclops X-15 spotlight instead of sun. In the images above - which are just versions of one photo - there seem to be two short arcs that match the location of the Kern arc as shown by the simulation.

The simulation (Jukka Ruoskanen's simulation software) is made for light source elevation of 0° which must be very close to the real situation. Thick h/d 0.6-1.0 regular hexagonal plates with tilts of 2° were used for the Kern arc. Thinner plates made also good Kern, but they produced additional circumzenith arc which is not seen in the photos.

In the first days and nights of diamond dust making in Kilpisjärvi we practically encountered every possible mishap. This was one of those nights. For one thing the blocker was not properly in place which resulted in lens reflections. Even worse, the lamp suddenly dimmed when the photo was taken: the battery that was supposed to be full had failed us.

So I had to increase exposure heavily afterwards in photo editing software to light up the dark photo. This resulted in excess noise and horizontal lines. To reduce the noise, mirror images of the photo were stacked ("flip and stack"). More natural versions are also given.

Upon experimenting with various crystal tilts and aspect ratios in the simulation program it became clear that Kern arc was always prominently accompanying the circumzenith arc around 0° light source elevations. From that point of view there is nothing special in Kern showing up in the photo: it must be there.

Complex halo display in Destne

One of the most striking halo displays of recent years in the Czech Republic was observed on December 25, 2007 in Destne in the Orlicke Mountains. Diamond dust halo phenomena highlighted the sky shortly after 12 local time (CET) and lasted until sunset.

While skiing, Radek Svoboda took several shots with his cell phone camera and captured a variety of halos including ones like Tape arc (Parry supralateral arc) and heliac arc, as shown by the photo beside. See also another image.

After the inspection of rest of the photos, even diffuse arcs turned up.

Some of the images are featured in the gallery, other uploaded halo photographs of Czech observers can be instantly browsed on the latest uploads page.

Text: Tomas Trzicky

Well defined Moilanen arc in Viitasaari

On 23 January Jaakko Tähti was doing product photography in a factory in Viitasaari when he got a phonecall that there was a good halo display in the sky. He could not get outside but had a look at the display from factory window. An hour later, at 13:45, Tähti finally got a chance to go out and took photos from which the above panorama was made.

The halos in the display are the usual ones for snow gun generated displays (ski center was nearby), but the razor sharp form of the Moilanen arc is of a better class. Crystal samples from these kind of appearances could be useful in unveiling the mystery that shrouds the Moilanen arc formation.

Here are four single photos of the display ( 1 - 2 - 3 - 4 ).

Making halos in Kilpisjärvi

On 19th January the four of us, Jukka Ruoskanen, Marko Mikkilä, Ágnes Kiricsi and Marko Riikonen gathered at the Kilpisjärvi biological station in northern Finland to make halos. We had got some evidence that weather conditions in the Kilpisjärvi area might be favourable for ice crystal formation as long as the nuclei are provided. At his home, Marko Mikkilä had already done successful initial experiments of creating halos with a mixture of kaolin and water sprayed in the air, and this time we wanted to do more tests on the system.

During our one-week stay, we were able to create displays on two days and three nights, the temperatures being around -20 °C. The diamond dust cloud that developed seemed to be kilometres wide. This was accomplished with only about 10 litres of water and two spoonfuls of kaolin. The crystal swarm usually lasted about half an hour and then it was time to go back to spray more ( 1 – 2 ). On one night we succeeded in making halos 12 hours continuously.

We also tested a snow blower. A good display had been observed ten years ago in Resolute Bay created by such a machine (see drawings in Sivuaurinko 3/98 on pages 9 and 10). Our impression was, however, that it was not nearly as good as kaolin, and we eventually quit using it.

Mostly we had plate displays ( 1 - 2 ), but on two nights at the beginning of the favourable conditions there were also halos from column and Parry oriented crystals. Diffuse arcs and upper sunvex Parry arc were seen. Moilanen arc was present only on one night for a short while.

We also tried spraying water mixed with montmorillonite (also known as bentonite) on one day and managed to create a weak plate display. This clay mineral is referred to be an even better nucleator than kaolin, but we found its use problematic because of its clumping habit.

After each spraying round photographing the halos was sort of a hassle, there was not much time for fine tuning. The next step in halo making is to have a continuous automated feed of the nucleating mixture. Then the real fun can start.

Text: Ágnes Kiricsi, Marko Riikonen

Kern arc photographed in Finland

On the 17th November I drove 250 kilometers to the town of Sotkamo to check if there were any diamond dust halos. Two weeks earlier I had made the same trip, but the snowguns hadn't produced any halos. This time, however, the ski resort was surrounded by a thick fog cloud in which diffuse halos were visible.

I started searching for a better spot and after a while of driving the cloud started thinning. 22º halo, parhelia and M-arc were present and I took ice crystal samples before continuing the search. Several kilometers later it started looking really good and I stopped the car by a field where the view was unobstructed.

The parhelia were extremely strong, and I made my first observation of 44º parhelia. Other halos were 22º halo, sunpillar, subsun, subparhelia, upper tangent arc, circumzenith arc, 120º parhelia, 46º halo, parhelic circle and M-arc. The 120º parhelia looked like fuzzy pillars.

I took several hundred photos and ran out of memorycard. Luckily I had an old camera with slide film, but as it also ended pretty fast, the only solution was to get a new memorycard from the local town over 10 kilometers away. When I was back, the display was still going on, but the new card also got filled up in half an hour. So it was time to get home.

Next day, as I was having a closer look at the photos I couldn't believe my eyes what appeared on the screen. The circumzenith arc had a faint extension going all around the zenith: the Kern arc. See this photo, which also shows reflected Lowitz arcs. In some of the photos the 46º halo has an angular appearance revealing the 46º contact arcs , which were first photographed in Muonio a year ago ( 1 - 2 ).

Although readily appears in simulations, the Kern arc has been controversial because of the lack of photos. It was first reported by H.F.A Kern in 1895 in the Netherlands and at least six subsequent reports are known. As an explanation for Kern arc formation, raypath 1-3-5 in plate crystals as well as multiple scattering has been suggested. In the Sotkamo display there were 44º parhelia indicative of the latter, but it is not certain whether this mechanism is applicable higher up in the sky where the crystal cloud is optically much thinner.

Single scattering raypath 1-3-5 produces Kern arc easily, especially when the crystals are towards triangular shape and the sun is low. Both of these circumstances were realized in the Sotkamo display where the sun elevation was six degrees and a considerable number of crystals were semitriangular. As for crystal aspect ratio, it is thick plates that are favourable for Kern arc formation. The crystals in the photos seem to be below optimum thickness, but it should be noted that the crystal samples were collected before the peak of the display when Kern arc was not yet occurring and thus the sample may not fully representative.

The simulation of the display was made with populations of plate, Lowitz and column crystals. Fixed multiple scattering probability (0.15) was applied for all populations. Plates were semitriangular and the Kern arc in the simulation is primarily from single scattering 1-3-5 raypaths. Multiple scattering makes the 44º parhelia. Poorly oriented spinning Lowitz crystals made the 46º contact arcs and Lowitz arcs. It is noteworthy that the apparent 22º halo in the simulation is actually made of Lowitz arcs, which may also have been the case in the display. Columns made the weak 22º upper tangent arc. The simulation was made with a program by Jukka Ruoskanen

During recent years we have seen photographs of numerous displays with very bright parhelia. It is probable that at least some of them involved the Kern arc. This might be worth keeping in mind when the next bright plate crystal display comes along.

Halo and northern lights

Some ten years ago or so my friends and I went though Finnish Meteorological Institute automatic northern light camera films in search for moon halos. At that time I considered the northern lights as unnecessary noise that disturbed the distinction of halos on those low resolution 8 mm films.

Last Thursday I was photographing a moon halo display in Kilpisjärvi biological station, when suddenly green northern lights moved fast across the halos. It was a rather nice treat and above is one photo of those moments.

Also a 9° halo was in the sky on that night, as shown by this photo. Two nights later the 9° halo reappeared, but the display was much poorer.

Moilanen arc and diffuse anthelic arcs in Prichovice

A superb halo complex was observed by Petr Kousal on December 25, 2007 in community of Prichovice. He observed 22° halo, parhelia, pillar and also bright upper tangent arc with sunvex Parry arc. Except for these quite frequent phenomena he observed also Moilanen arc, which tips almost touched the 22° halo ( 1 - 2 - 3 - 4 ).

The best event came when he looked towards anthelion point, where diffuse arcs were clearly visible. This observation of diffuse arcs is the first in the Czech Republic ( 1 - 2 - 3 ).

This display was also captured by Martina Pistorova during her afternoon walk to the outlook-tower Stepanka in Prichovice ( 1 ). Analogous halo complex with Moilanen arc was also observed and photographed by Frantisek Kovarik in community Prichovice ( 1 ).

Also Hana Koukalova observed halo complex in the same community. Faint heliac arc is maybe displayed in one of her pictures ( 1 - 2 ). And finally, also Julia Vachkova observed a few halos together with infralateral arc ( 1 - 2 )

Text: Martin Popek, Lukas Shrbeny

Moilanen arc in Paprsek

In Czech mountains Ivo Bartos observed diamond dust halos on December 23, 2007 near ski area of Paprsek, which is situated in the highest Moravian mountains.

From 2 to 5 pm he most of the time observed sun pillar and parhelia with fragments of 22° halo. Culmination of the phenomenon occured at 4 pm when Moilanen arc appeared. This is the fourth observation of this arc in the Czech Republic.

The first Moilanen arc in the Czech Republic was observed by Ivo Brezina in January 2003 in Horni Misecky along with other bright halos ( 1 - 2 ).

The second case was by Milan Martinek in Bozi Dar in February 2004, who, besides Moilanen arc, observed also upper sunvex Parry arc heliac arc and maybe Lowitz reflected arcs. The photos of the heliac arc were the first in Czech Republic. The third Moilanen arc was observed together with bright upper tangent arc by Emil Brezina on January 1, 2006 in Vsetin.

Also Moilanen arc observed by Jan Bim on December 20, 2006 in Austrian Alps is noteworthy ( 1 - 2 - 3 ).

Text: Martin Popek, Lukas Shrbeny

Two Parry arcs in Ohio

While at work prior to leaving I was outside and happened to look up and saw nice wide tangent arc spreading out. Inside it was a convex Parry, the first decent one since 2000. As I watched and shot photos I could see the more common concave arc and there was also faint supralateral arc and circumzenith arc.

I also visually could see Lowitz arc curving down from upper concave Parry arc and circular lowitz arc near the sunvex arc touching the 22° halo. What a way to start the new year for halos. It was nice to see both Parrys at once. Photos were unsharp masked to enhance the halos.

Text: Michael Ellestad

The arms of parhelia and subparhelia on the Pansky Vrch hill

On December 23, 2007 (1:40 – 3:50 pm) Ladislav Nyc observed during his afternoon walk bright halos in diamont dust. When he went up from inversion cloudiness to see sunrays, on the hill of Pansky Vrch a great spectacle came along. Except for frequent halos like pillar, 22° halo, parhelia and upper and lower tangent arcs also subhalos were visible: bright subsun and subparhelia with arms of parhelia. These arms of parhelia, which join subparhelia and parhelia of 22° halo, are the first ones observed in the Czech Republic. More photos ( 1 - 2 - 3 ).

Also Stanislav Bernard in Sedlonov saw halos during his walk around Orlicke hory, mountains in the north part of the Czech Republic ( 1 - 2 ).

Text: Martin Popek, Lukas Shrbeny

Moon halos in Pec pod Snezkou

On December 23, 2007 from 6 to 7 p.m. local time Lubos Brat observed bright Moon halo complex. 22° halo, complete paraselenic circle, upper and lower tangent arcs and circumzenital arc dominated the display (see a composite image). In addition to these quite frequent halos also upper suncave Parry arc, 46° Parry arc and helic arc were present, as shown by the photo above.

Lower component of the Lowitz arcs may be present as a vague brightening on the 22° halo (right side), see this photo. Lubos Brat observed also halo phenomena in the artificial light and he was the first person in the Czech Republic to take a photo of superparhelia.

More photos of halo phenomena observed in Pec pod Snezkou between December 22, 2007 and January 5, 2008 are available on the Lubos Brat web site Altan Observatory.

Daytime halos were also seen on the 23 December. In the Orlické mountains Hana Tesarova photographed a display with bright circumzenital arc ( 1 – 2 ).

Beautiful circumzenital arc was observed also on December 16, in Western Tatras mountains by Boris (Slovakia), see photo here.

Text: Martin Popek, Lukas Shrbeny

Moilanen arc in Mátraszentimre, Hungary

This photo shows the diamond dust display near Mátraszentimre skiing resort in Hungary on 30th December and was taken by photographer Zsuzsanna Tóth. The snow guns were on, and the halo appeared in the early afternoon and lasted about an hour. The display was the best at around 2 p.m. Then the 22° halo, parhelia and upper tangent arc were accompanied by a Moilanen arc. As indicated by the bright parhelia and a less conspicuous upper tangent arc, the display must have been dominated by plate crystals. Unfortunatelly, however, there was no one around who would have collected samples, so the mystery remains unsolved.

Natural diamond dust is very rare in Hungary, due to our temperate continental climate. But this winter has so far been much colder than the average ones, and it has resulted in a pretty diamond dust display without the assistance of any snow guns on 3rd January in Mogyoród. Alexandra Farkas took this picture of UTA, CZA, and supralateral arc. The halos don't show anything extraordinary, still it was a unique sight in Hungarian winter.

Circumhorizon arc in Vítkovice

When I first saw photos by Vaclav Fego captured on December 22, 2007 in Vitkovice in Krkonose mountains I told myself just one thing – wow, that is amazing, I haven’t seen anything similar for a long time! On the images of this Moon halo display is visible bright and colorful circumhorizon arc together with short projections of infralateral arc low above the southern horizon. Also 22° halo with Parry arc and full paraselenic circle are seen. Here is one photo pointed at higher up in the sky and here is a composite image.

The situation captured on the photos is similar to this simulation, made with Halosim by Les Cowley and Michael Schroeder

Circumhorizon arc appears when elevation of the Moon (or Sun) is 58° or more above the horizon. In this case the elevation of the Moon was 66°, which is several degrees more than that of the Sun at noon at summer solstice in the Czech Republic (the inclination of the Moon’s orbit to the ecliptic can position the Moon 5° higher)!

In the same day there was also nice complex display around the Sun:

From Bedřichov u Kralovky, photo by Vladimir Wasserbauer and from Paseky nad Jizerou, photo by Čenda Jirak.

Text: Martin Popek, Lukas Shrbeny

( addition on 10 Jan: more images by Vaclav Fego: 1 - 2 - 3 )

Diffuse arcs with anthelion on Humlnet webcam

A strange white faint arc appeared on December 17, 2007 on webcam in Pec pod Snezkou, Czech Republic, operated by Humlnet network. Because the webcam is oriented northward, there was a suspicion that at least anthelion could be captured on the photographs. Fortunately, there is an image archive available, so we were able to create stacked image. I used 10 images with apparent anthelion for processing in Registax. The result revealed together with anthelion also quite bright diffuse arcs.

There are another 2 examples of webcam images with halos: Parhelion captured by Hydronet webcam in the Jizera Mountains on December 13, 2007.

Infralateral and supralateral arcs on Humlnet webcam in Zacler (December 25, 2007).

Text: Martin Popek, Tomas Trzicky

22° halo on snow surface with horizontal color segments

This 22° halo was seen on a thin snow layer which formed on a freshly frozen river from power plant induced precipitation and freezing mist. The dark area inside the 22° halo is prominent, indicating well developed solid crystals that scatter light only at halo angles.

The photo shows also broad horizontal segments of cyan and magenta in the outer areas of 22° halo. These segments seem to be very sensitive to the variations in the camera positioning, changing their position relative to the 22° halo and ground features, as shown by other photos taken by Peter Vancoillie.

I have no explanation to offer. The display was seen in Ghent, Belgium on 21 December 2007.

A diversity of surface halos in Juva

It is not unusual to see a 22° halo glittering in separate crystals on snow surface. The display that Jari Piikki observed on 22 December on a frozen lake surface is of a better quality. Towards the sun there were the parhelia and perhaps segments of a 22° halo, as shown in the photo above. Two close-ups are also provided: image 1 and image 2. In image 1 the close-up area of image 2 is marked with two white lines.

Piikki took photos of the responsible ice crystals. They seem to be frost crystals, which top ends has plates grown horizontally. See here and here. Crystals are large; the photos were taken with a standard lens. Some crystals show possible cavities.

The halo display on the ice surface was changing as one moved on the ice. This image shows faint extensions from the parhelia towards the observer. The display does not seem symmetrical, but slightly distorted towards right. This could be caused by uniform atsimuthal orientation of the crystals prisms. At least the crystal photos give an impression of all crystals having similar orientation. This is clear evidence that crystals are frost crystals, not fallen from the sky. Locally inclined surface may also be affecting the halo features. The image with parhelia extensions was taken with camera lens touching the ice, features close to the camera are thus formed in small surface area. Preferential atsimuthal orientation of crystals may be more likely in small than large surface area.

Opposite to the sun a white glow was seen at the subanthelic point (photo taken with camera on tripod). Airborne plates do not produce such effect, at least in simulations. Reflecting complex ice surface or/with frost crystals here must be chancing the rules so that the glow can be formed. Could this be called just a heiligenschein?

At around 120° from the sun on both sides white brightenings (arrow) were observed, indications of 120° parhelia. In airborne crystals the usual 1-3-4-2 and 1-3-4-2-1 raypaths for 120° parhelia and subparhelia are not effective at very low sun elevations, but in frost crystals external reflection from ice surface may allow these raypaths. In airborne crystals other raypaths can make 120° parhelia at low sun, but crystals deviating from regular hexagonal shape are required. Here the frost crystals seem to be pretty regular in shape.

Halos were also observed at the nadir region. These are possibly patches of a circumzenith arc caused by light reflection from ice surface. The colors, on the other hand, seem similar to the halos from 60° refracting angle. According to the observer, sun is most likely towards the upper left corner in the photo.

A question remains whether these halos should be called with sub -prefix or not. This has some significance, because sub-120° parhelia and sub-circumzenith arc (or circumnadir arc) has not been observed yet. Subhalos from airborne plate crystals are characterized by a reflection from bottom basal face. Here the bottom basal face needed for the subhalos formation may be missing or is only partially developed as crystals are at attached on the ice.

Most likely the formation of the halos is to greater amount contributed by a reflection from ice surface before or after the rays enter or exit the crystal. If we take it that a subhalo must arise from ray path fully inside one crystal, then these are not subhalos.

Marko Riikonen, Jarmo Moilanen

Parry Arcs Over Central Europe

December 22nd was a day of complex displays over Central-Europe. While Hungary was covered with thick fog, mountain peaks above 900m witnessed sunshine and favourable conditions for halo-formation. Attila Kovács took the photo of the suncave Parry arc on Bálvány in the Bükk Mountains 956m above sea level. The display started with bright parhelia that appeared at 12:05 UT and lasted about half an hour. At around 12:30-12:40 the complex display began to emerge. First the 22° halo with the upper tangent arc. Altogether, a 22° halo, parhelia, UTA, a long section of the parhelic circle, CZA, supralateral arc and the sharp suncave Parry arc were visible. The Parry arc lasted about 5-10 minutes. There is unfortunatelly no report about the anthelic side.

Although the Czech Republic is two countries away towards the northwest, the distance is not that great for crystals forming a display in high clouds, especially that the Hungarian Parry observation was made in the north of the country. On the very same day Martin Popek photographed an attractive sunvex Parry in Nýdek.

Diamond dust display with a possible new halo

On the evening of 22th December weather conditions finally changed to better. Humidity was up with temperature around -8°C. At the Louekallio ski-resort snow guns produced a crystal cloud and action lasted few hours until crystals suddenly vanished.

Singly oriented columns dominated the swarm. With HID-modded Cyclops Thor Platinum X-15 lamp the display looks quite the same what we have seen already in haloreports, except that there is weird spots on both sides of the upper tanget arc (photo above, see also enhanced image). They seem to extend through the 22° halo towards the lamp, but this may be due to divergent light. In simulations arcs that bear some resemblance to these spots can be produced with slightly tilted Parry crystals, but we certainly need more photos to say what is going on.

Also Moilanen arc appears in the photo. At first glance it may seem to be
connected with the new effect, but closer look reveals they are two separate halos. Diffuse arcs were observed opposite to the lamp.

In the moon light, circumscribed halo, infralateral arcs, 46° halo and full parhelic circle were seen. The long Wegener arc, which continues close to infralateral arcs, was not seen visually. See also another photo of this stage. Later on ice crystals turned to be more randomly oriented. Moon elevation was 52°.

Similar column dominated display was also noticed by Arto Oksanen in Muurame. See his photos here. When 0ksanen first noticed the display, there was Wegener arc above the parhelic circle and he hurried for the camera. Unfortunately, the best moment was gone when he was back. "By the time I got camera from inside, halos had weakened and of parhelic circle only a trace was visible", Oksanen tells.