Subsun

subsun

A halo in the form of a bright white spot as far below the horizon as the sun is above it.

The subsun is explained by reflection by the horizontal faces of oriented ice crystals (e.g., large hexagonal plates). Such crystals are never perfectly horizontal with the result that the shape of the subsun changes slightly with solar elevation, being circular for high suns and increasingly teardrop-shaped for low suns.

Copyright 2022 American Meteorological Society (AMS). For permission to reuse any portion of this work, please contact [email protected]. Any use of material in this work that is determined to be “fair use” under Section 107 of the U.S. Copyright Act (17 U.S. Code § 107) or that satisfies the conditions specified in Section 108 of the U.S.Copyright Act (17 USC § 108) does not require AMS’s permission. Republication, systematic reproduction, posting in electronic form, such as on a website or in a searchable database, or other uses of this material, except as exempted by the above statement, require written permission or a license from AMS. Additional details are provided in the AMS Copyright Policy statement.