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Lunar odd radius display in diamond dust


On four out of last five winters Tapio Koski has photographed lunar diamond dust odd radius halos in the Rovaniemi area. These one-per-winter occurrences are almost solely responsible for lunar diamond dust odd radius displays photographed in Finland during those years. This winter we wanted take part in the tradition. Yet despite numerous odd radius displays we had harvested in the beam, those by the moon – or sun for that matter – were simply not on the offing.

Except on the night of 20/21 January, which was the month’s last diamond dust night in Rovaniemi. During the day, when driving in the city, we paid attention to Fairbanksian amber, a beautiful yellow glow in the sun direction which can be seen in cold weather and with which we became familiar on the succesful halo expedition to Fairbanks in January 1996. This gave us an omen of foreboding that a night of big odd radii diamond dust was finally on the cards for Rovaniemi. Weather forecast was with us too, as the temperature was expected to drop to -33° C – the magic number that Walt Tape has given as being in the center of the temperature range favorable for odd radii.

The display appeared as some thin water cloud that had momentarily overtaken the sky cleared away. The first halo visible was upper 23° plate arc, many others soon followed the suit. In the beam only a crappy plate dominated display was visible – the pyramid stuff was higher up.

Authors: Jarmo Moilanen, Marko Riikonen, Finland

Airglow – When a „green aurora“ turns into an even rarer phenomenon

During the night from July 14 to July 15, 2012, Tilo Schroth could observe and photograph in northern Saxony, Germany this rare phenomenon: “Chasing aurorae from northern Saxony is full of surprises. You are burning the midnight oil in the middle of nowhere during nights which potentially might bring a touch of aurora, pressing the release from time to time, controlling the monitor display, and then looking up to the sky again. A shooting star here, a small satellite there…there is a lot to see during those nights. The same was it during the night between July 14 and July 15, when the solar wind was about to hit earth directly. We were three persons on the Liebschützberg range (except from some couples in love). We were just about to call it a day when a slowly increasing green loom appeared on our monitors. At that moment I still was connected to the Meteoros-forum, but a short while later the storage battery of my mobile phone showed empty.
My two friends and me on the hill were sure that this was a green aurora. So we were very excited. We were not connected to the forum any more, where somebody already had talked of “airglow”. Nevertheless, we were not disappointed when learning that our guess was wrong the next day.
What we saw – and could not really interpret – was really airglow. Appearing as a grey veil to the naked eye, our reflex cameras reveiled its real structures.”

“Airglow” is the name for a faint, lamellar glowing of the night sky which is induced by electromagnetic radiation. In normal cases, this diffuse glooming can hardly be perceived, but its brightness can be influenced by strong ionospherical activities. So airglow could not only in this case be seen in connection with solar wind and aurorae. The latter were visible over Germany also in this night, but just very faintly.

An interesting fact is the far southward extension of the airglow shown on a map made by Stefan Krause, which shows all observations. This is probably due to the fact that in Northern Europe it does not really get dark at this season. So parts of the atmosphere might get some sunlight which may intensify the airglow.

In the Meteoros-forum are more pictures from this rare phenomenon.