Concave & convex Parry arcs photographed in Georgia

A visitor of my homepage emiled me this photo of a complex display that took place in Rome, Georgia and the year I can't remember but it was in the early 90's and of all the halos the bright upper concave and convex parry arcs are the most interesting. This is probably the best I have seen where both upper parry arcs are visible . Other images show a bright supralateral arc as well. The person who sent the photo is Loren Hall and his email is: bctimebandit@earthlink.com

46° contact arcs

About a year ago in Muonio, Finland, a diamond dust display produced a new halo, the 46° contact arcs. The display was shortly reported in the blog, but no simulation was shown. So here is a simulation, together with a composite of the photos that were taken by Päivi Linnansaari. The 46° contact arcs, which arise from Lowitz-oriented crystals, appear as three arcs below the circumzenith arc.

The Lowitz crystals used in the simulation are regular plate-like hexagons, with aspect ratio of 0.4, tilt about the Lowitz axis 28° and Lowitz axis rotation 1°. Sun elevation is 9°. The Lowitz arcs themselves are faintly visible at 10 and 2 o'clock positions, separating from the 22° halo and reaching towards the upper sunvex Parry arc. This is the circular component of the Lowitz arcs, also known as the c-component (after Greenler).

Occasionally, in high cloud displays there is seen a short patch of 46° halo under the circumzenith arc, as shown here in the photo by Stepanka Kosova, taken on 20 August in Prague. It has been sometimes suspected that these might be indications of 46° contact arcs. Whether that's the case, it may be confirmed if a series of photos are taken for stacking.

The simulation is made with HaloSim by Les Cowley and Michael Schroeder.

Concave and convex Parry arc in Germany

When Stefan Danner was driving home in the evening of September 12th, he saw a pair of very beautiful sundogs. After having reached home, he noticed that there were two more halos – a very rare combination of a concave and a convex Parry arc. He could watch the two arcs getting brighter and brighter by the time. The impressive phenomenon lasted about 10 minutes before it ended showing a bright sundog.

Later, when he looked at the “raw pictures” closely, disenchantment followed: there was not a lot to see for the eyes of a layman. Only after having processed the pictures a little more or less, the effect of the halos in the pictures was like he felt it. (He saw them better than visible in the “raw pictures”, but not as intensive as they look after the processing.)

More pictures

Moilanen arc display with cell phone camera

Jaakko Tähti photographed this moderate display with Moilanen arc on 12. January 2007 in Viitasaari. "The halo display lasted for about four hours and changed constantly. It was a pity I was working inside. At times however I went to take some pics", says Tähti who used his cell phone camera for photographing. The vague double structure in the upper tangent arc seems to indicate that the display contains also an upper sunvex Parry arc.

The following night diamond dust was drifting also in Tampere and Hyvinkää. See the divergent light halos by Jari Luomanen and Jukka Ruoskanen.

Diamond dust from Riihivuori snow guns

Towards the last weekend tension was rising among Finnish halo observers. It was going to be clear skies with sinking temperatures and full moon. Most of the ski centers had their snow guns running, so anticipation for diamond dust was high.

On Saturday, 4 November, Arto Oksanen drove to check the sitation at Riihivuori ski center. There was indeed a column crystal dominated display with upper sunvex Parry, as shown in the photo on the left.

Next night Arto did not have to go anywhere, since wind carried the ice clouds straight to his doorsteps, to Muurame town. It was Parry-time again, and now in addition to normal upper suncave there was also the much less commonly seen lower sunvex Parry (photo on the right). Untill the last winter the latter has been considered as an extreme rarity, but now reports have increased, thanks mainly to ski centers' snow guns and active observers around them. The display contained also other halos of interest, like Wegener anthelic arc and anthelion. See also Juha Oksa photos from Muurame the same night.

Parry sunvex and suncave arcs

On October 28 in Czech Republic I and Lukas Kosarek observed Parry arcs. I saw sunvex arc too (you see title photo) and Lukas take photos of Suncave arc. We saw a nice supralateral arc also.