Icy window corona

At the beginning of this winter season at a cold morning - dark outside - with a thin layer of hoarfrost on the inner side of the bus windows I've noticed that the light of the street lamps' light was not simply scattered on the windows, but having colorful corona around them. At that time I had no camera with me… All along the winter I was waiting for the same display each morning when some ice was on the bus windows, but for long weeks I haven't met with such spectacular phenomena again.This day was my day on 24th January. Very thin layer of frost was on the inner part of the windows, (with some frost ferns too by the corner of the window frame), mainly this layer was made of small uniform ice crystals made of frozen vapor droplets, we might call it an ice film, it was about 0,1 mm thin.All the lamps outside had a corona, no matter how far the lamp was.The street lamps with white light had the most beautiful color range, the orange colored light of sodium vapor lamps had a less distinct colors and they were a bit moved towards the reds. Not only the street lamps' corona was seen on the ice layer, but a much less spectacular corona around the reflection of the inner lamps of the bus too! At the part of the frost ferns pattern the corona became irregular in shape. When the lamp was near the window I could also see the bigger outer rings of the corona. Almost the same phenomena appears when simple water vapour is on the windows, but that one is really less poor in colors compared to the ice film corona.This was the first time when I could take photos of a corona produced by ice crystals. It's a pity, I could not take close-up photo of the ice layer itself (the bus was driving me to work so it was permanently moving).

Photos are collected here: The only afterwork was some noise reduction and size reduction. It was totally dark outside, so the pics were taken with ISO200 - ISO400; aperture F4 - F5,6; exp. 1/15 - 1/25 sec. auto white balance; without tripod or any kind of help to avoid moving.I wonder if the same phenomena would appear if the outer side of the windows would have a layer of hoarfrost on it. It's only weather's turn to show it up!

Author: Monika Landy-Gyebnar, Veszprem, Hungary

"Subsun" upon ice crystal

While taking the photographs of the iridescent fissures in the ice, I noticed some beautiful ice crystal structures on one of the puddles. When I looked at them more closely, I saw intensive reflections of the sun in them. Animated by the hoar-frost halo I discovered before, I got the idea to photograph the reflection of the sun as a kind of “subsun”. To get the reflection completely into the picture, it was necessary to make a macro of the ice crystal. However, the crystal turned out ot be a lot more complex than I thought.

The reflection of the sun, however, was not a homogenuous surface, but appeared to be a slightly oval shaped, speckled white spot with a broad golden and also speckled rim. It is exactly this reddish-golden rim that gives me quite a headache, reminding me a lot of the reddish coloured fringes which sometimes can be seen at other haloes like parhelic circle or 120°-sundogs. The sequence of colours and the outward manifestation is that of a common aureole. However, in this picture it looks as if the colour came out of the inside of the ice crystals. Especially take a close look at the crystals marked with arrows.

About one week later at another frozen puddle, the reflection of the sun again had a reddish rim. But here the situation is quite different. This time it is a fragment of the frozen water surface. The wind has carried dust upon the ice which with the help of the sun had smolten innumerable tiny holes into the surface which originally had been smooth. Low temperatures then had made it freeze again. All in all, these processes have caused a rather permeable surface structure to develop, so the reflection of the sun is more like a diffraction. Especially in its upper part, there is an indication of iridescence. Who knows, on day somebody might succeed in taking photographs of “ice surface coronae”!

Last but not least: Of course you can also try to take a fragment of ice off a puddle and make some experiments with it. Maybe there will be confirmations of these sightings pointing also out to the possibility of a (additional) light refraction in the red rim.

Author: Reinhard Nitze, Barsinghausen, Germany