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Trumpet (flared) Pillars

(1-3) Sigulda, Latvia Dec 28, '08 imaged by Aigar Truhin.

(4-6) Deventer, The Netherlands Jan 8/9 '09 images by Peter Paul Hattinga Verschure.

The pillars apparently shining upwards from unshielded bright lights on very cold nights are generated by column shaped ice crystals drifting in the cold air with their long axes nearly horizontal. The crystals are not actually above the lights but are but are between them and you.

Most pillars are generated by plate shaped crystals and these here are unusual in that they come from other crystals and the pillars themselves have trumpet-like curved tops.

Ordinary plate crystals are not able to produce trumpets. More on how the flared shapes were generated is in a later OPOD, suffice to say here that column crystals were almost certainly responsible. Horizontal column crystals were present in the Netherlands display as evidenced by the circumscribed halo around the Moon (image 4) and Peter Paul Hattinga Verschure saw traces of upper tangent arcs at the top of 22 degree halos around nearby street lights.

Aigar Truhin imaged one of his pillars at 30 second intervals to produce the sequence in (3). The first frame shows a weak pencil shaped pillar and 30s later there is instead a weak trumpet. The next frame has a strong pencil and a trumpet then shows in the next two frames. The last two images show that the trumpet position and extent depends on the spatial location of the crystals.

Peter-Paul's image (6) shows trumpets from very close and identifiable lights.
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