Blue spot on the parhelic circle

Mika Sillanpää*, Jarmo Moilanen, Marko Riikonen, Marko Pekkola

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

3 Citations (Scopus)


We develop a theory for a new effect on the parhelic circle. We show that there is a colored segment on the parhelic circle at a certain large azimuth that depends on solar elevation. The color segment appears at solar elevations below 32° and is explained as a transition between total and partial internal reflection in the main ray paths of the parhelic circle in oriented ice crystals. Based on our simple refraction theory and computer simulations, we find that the color of the segment is mainly green and blue. The theory is tested with available photographs of the effect.

Original languageEnglish
Pages (from-to)5275-5279
Number of pages5
JournalApplied Optics
Issue number30
Publication statusPublished - 20 Oct 2001
MoE publication typeA1 Journal article-refereed


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