46° lateral arcs

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46° lateral arcs

A halo in the form of arcs in the vicinity of the halo of 46°, the form of which changes markedly with solar elevation.

Sometimes given the names supralateral and infralateral, depending on whether the arcs are mainly above or below the sun. The supralateral arc appears to the sides and above the halo of 46° when the sun is low; it is concave toward the sun but vanishes for solar elevations above 32°. The infralateral arc can be either convex or concave. For some elevations, either arc may or may not be tangent to the halo of 46°. These arcs are explained by refraction through the 90° prism ends of columnar ice crystals oriented with their long axis horizontal.


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