February - halos You are here: Home Photo gallery Atmospheric optics Ice crystal halos Infralateral arcs

Infralateral arcs are two arcs to the lower left and lower right of the sun, at a minimal distance of 46 degrees, and curved outward. They are produced by light being refracted through pencil-shaped, horizontally aligned, ice crystals. Light enters one of the vertical end faces and exits a side face. The freedom of rotation along the crystal's horizontal axis yields an arc instead of a parhelion. (the parhelion which would result, if the crystal would have the Parry orientation, i.e. horizontally aligned with the base face also horizontal, is referred to as a Tape contact arc to the 46 deg. halo).

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