Origin of the anthelion
نویسنده
چکیده
Pt. Schwartz University of Texas, Austin, Texas 78712 (Received 22 August 1977; revision received 30 January 1978) The formation of the anthelion is discussed. Previous theories by Bravais, Humphreys, and others are shown to be imcompatible with observation, or highly improbable. An explanation is set forth in which the anthelion is formed in common hexagonal columns with the c axis horizontal and with two side faces vertical. Light enters an upper oblique face, is reflected twice by the end and opposite vertical face, then emerges from the crystal through the lower oblique face on the same side of the crystal it entered. In agreement with the observations, this mechanism produces no anthelion when the solar elevation is greater than 46'.
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