Definitions

Liljequist_parhelion

Liljequist parhelion

A Liljequist parhelion is a rare halo, an optical phenomenon appearing on the parhelic circle approximately ±150-160° from the sun between a 120° parhelion and the anthelion (opposite to the sun at the antisolar point).

While the sun touches the horizon, a Liljequist parhelion is located approximately 160° from the sun and is about 10° long. As the sun rises up to 30° the phenomenon gradually moves towards 150°, and as the sun reaches over 30° the optical effect vanishes. The parhelia are caused by light rays passing through oriented plate crystals. Like the 120° parhelia, the Liljequist parhelia displays a white-bluish colour. This colour is, however, associated with the parhelic circle itself, not the ice crystals causing the Liljequist parhelia.

The phenomenon was first observed by Gösta Hjalmar Liljequist in 1951 at Maudheim, Antarctica during the Norwegian-British-Swedish Antarctic Expedition in 1949-1952. It was then simulated by Dr. Eberhard Tränkle (1937-1997) and Robert Greenler in 1987 and theoretically explained by Walter Tape in 1994.

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