Free Halo Simulation Program
© Jukka Ruoskanen 2010
Pälkäne, 22nd January 2006
Photo by Jari Luomanen *
Lowitz arcs have received a lot of attention by halo scholars in scientific literature. Less noise has been made of a frequent diamond dust visitor - reflected Lowitz arcs.
Jari Luomanen's photo is a good representative of a winter display including reflected Lowitz arcs, the two faint halo arcs rising upwards from both parhelia. The simulation trial is started with thin plates which are allowed to tilt 10-20 degrees about the Lowitz axis. This display was simulated with 15° tilting angle and mean aspect ratio of 0.1 (Gaussian distribution with std = 0.05).
In the simulation one can see a slight mismatch in the inner reflected Lowitz component's curvature when compared to the photograph. The V-shape formed by the 3-1-5 and 4-1-6 -components is more opened in the simulation. Why there is such discrepancy is unknown. It is not probable that the projection of this fisheye lens would cause the difference. Maybe the theory concerning these arcs is not complete yet.
The 46° direction is out of the bounds of this photograph and simulation. Jari's other photos cover that region too and a solitary circumzenith arc is visible in the distance of about 46° from the Sun. However, when doing reflected Lowitz / Lowitz -simulations the 46° contact arcs can not be avoided. Still we have only a few known cases of these "46° Lowitz arcs". We don't know why that is so.
Try it yourself, and see if you can come up with an idea to correct the curvature of the 3-1-5 -arc and find a way to get rid of the 46° contact arcs in displays where they are not seen in photographs. The parameter file of the simulation above can be downloaded HERE.
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