ice halos and other optics

Streelight Bottlinger in Kangasala on 9/10 January 2010

If there is a holy trinity for a halo man, it must be the appearance of streetlight pillar and Bottlinger’s ring. The night we saw this with Jari Luomanen we had given alreaydy up the halo hunt at Sappee ski resort and were returning home. But on a way back Jari thought of seeing something resembling 22 tanget arcs in the Kangasala lights and we went to take closer look. It was not tanget arc – the lamp pillar was accompanied by a steep V-figure, of a kind which we had never seen before. We started photographing, although in the beginning we had swells of  suspicions of it being just a lamp artefact. However, as the effect later clearly showed on some other lamps, this was not a worry anymore: it was a halo. But what halo, that was not competely clear until later when the halonight was already over.

The stuff formed from nucleating water fog at -16 C. The area where the nucleation took place was perhaps about a square kilometer and within it, only at a small, say, two hundres square meter area was the Bottlinger seen. Elsewhere it was just pillars (the first photo above shows just pillars, but to the right from the photo a Bottlinger was seen constantly from a lamp only about 100 meters away). And outside that water fog was everywhere. Anyway, the Bottlinger was seen in the same spot for 4 hours at the Kangasal industrial area. We drove a bit around returning always to same place.

Some variation can be seen in the photos in the angle of the V when a time lapse movie is made. I took crystal samples and above are plenty of photos of those crystals. For some reason all turned more or less blurry, but one can still make out details of them.  Is it only me, or are the branches of many crystals slightly sloping towards the ends? That low angle would provide the reflecting surface for the Bottlinger in horizontal crystals.

Now Bottlinger’s ring is just a helic arc from crystal angles that do not deviate much from the horizontal, but in this display there was also another helic arc, as shown by two photos above. This one probably has the same angle as the normal helic arc from Parry crystals. Non-Parry helic arcs are common – they have been seen with only a pillar.

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