Intensity distribution of the parhelic circle and embedded parhelia at low solar elevations: theory and experiments

TL;DR

This paper combines theoretical modeling and experiments to analyze the intensity distribution of the parhelic circle and embedded parhelia at low solar elevations, enhancing understanding of halo phenomena.

Contribution

It provides a detailed geometrical optics analysis and experimental validation of halo features for ice crystals at low solar elevations.

Findings

Identified mechanisms for various halo features including parhelia and Liljequist parhelia.

Compared theoretical azimuthal coordinates with experimental data from a rotating glass prism.

Enhanced understanding of halo intensity distribution at low solar elevations.

Abstract

We describe the intensity distribution of the parhelic circle for plate-oriented hexagonal ice crystals at very low solar elevations using geometrical optics. An experimental as well as theoretical study of in-plane ray-paths provides details on the mechanism for several halos, including the parhelia, the $120^{\circ}$ parhelia, the blue spot and the Liljequist parhelia. Azimuthal coordinates for associated characteristic features in the intensity distribution are compared to data obtained using a rotating hexagonal glass prism.