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The 46{degrees} Halo and Its Arcs
Science (New York, N.Y.)
|November 9, 1979
Summary
Simulating light patterns from ice crystals reveals how different orientations create atmospheric optical phenomena like halos and arcs. This research explains the formation of various sky light displays caused by hexagonal ice crystals.
Area of Science:
- Atmospheric optics
- Crystallography
- Light scattering
Background:
- Ice crystals, typically hexagonal prisms, refract and reflect sunlight.
- The orientation of ice crystals significantly influences the resulting atmospheric optical phenomena.
Purpose of the Study:
- To simulate and analyze the light patterns produced by hexagonal ice crystals with various orientations.
- To understand the formation mechanisms of halos and arcs in the sky.
Main Methods:
- Computer ray tracing was used to simulate light passing through hexagonal prism faces.
- Simulations were performed for different distributions of crystal orientations and solar elevations.
Main Results:
- Randomly oriented crystals produce a 46-degree halo.
- Horizontal plate crystals create circumzenithal and circumhorizontal arcs.
- Horizontal column crystals generate supralateral and infralateral arcs.
- Spinning plate crystals form arcs near the 46-degree halo.
Conclusions:
- Crystal shape and orientation are critical determinants of observed atmospheric optical phenomena.
- Computer simulations effectively model the complex light interactions with ice crystals to explain sky light patterns.
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