Free Halo Simulation Program
© Jukka Ruoskanen 2010
Riihimäki, 5th June 2008
Photo by Jukka Ruoskanen *
Shade levels and number of rays affect the outcome of a simulation quite a bit. The simulation can look drastically different with the exact same parameters but with different number of rays and halo point shade levels.
This display was one of the few where all eight concentric rings can be seen in a single photograph. A huge area in Southern Finland enjoyed this marvellous sight. In order to make the 22°, 23° and 24° halos discernible in a simulation a shade level of 40 was chosen and number of rays was 3 millions. With these settings, and a correctly tuned pyramid crystal population, the rings can be separated.
When shade level setting is large, it is difficult to make the 23° plate arc as diffuse as it is in the photograph. The 24° lower plate arc is quite strong, and finding a balance between the well defined 24° lower plate arc and a very poorly defined 23° upper plate arc is difficult.
Four populations are used to simulate this display. Two of them have pyramidal ends and two are just ordinary prisms with plate- and random orientation. One of the pyramids constitute a random population, and the other a poorly oriented plate population.
The weak brightenings on the sides of the 9° and 20° halos have not been addressed in the simulation. What kind of a population is still missing? The parameter file of the simulation can be downloaded HERE.
[*]