Monday, 20 February 2017

Possible 46° contact arc in Jena, Germany

46° contact arcs are something of a true rarity. In the display shown above, photographed by Marco Rank yesterday in Jena, underneath the circumzenith arc is a concentration of crystals that could be due to one of the three components of 46° contact arc. 

Or maybe it is just a patch of 46° halo from poorly plate oriented crystals. Below I have made simulations with both scenarios. On the left is simulation with Lowitz crystals that give the 46° contact arc. It makes makes a somewhat better delineated effect than the 46° halo patch of the poorly oriented plate scenario on the right, and is perhaps more in accordance with the photo. 

Yet this is just one photo in a sparse crystal swarm and thus not quite enough to draw firm conclusions. Whether it is 46° contact arc or 46° halo patch (or something intermediate), it is anyway interesting to notice that the Lowitz simulation gives no discernible Lowitz arcs - and that they are not seen in the photo either.

Further below are simulation parameters for the Lowitz simulation. More photos of the display are shown in Marco's post in AKM forum.

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