Parhelic circle

From Glossary of Meteorology

parhelic circle

A halo in the form of a faint, white, horizontal arc at the elevation of the sun.

Small segments are more frequently seen than the complete circle. When caused by the moon, it is called the paraselenic circle. The parhelic circle is explained by reflection by the vertical faces of oriented ice crystals, such as the sides of large hexagonal plates, which also produce parhelia and paranthelia.