twilight arch

Quick Reference

The segment of coloured light that lies above the western horizon after the Sun has set. Although often poorly defined, it is initially almost semicircular with reddish and yellow tints, but goes through numerous changes of shape and coloration, until only a narrow segment—sometimes known as the bright segment or afterglow—remains above the horizon. A similar region and comparable changes are seen in the east before sunrise. See also purple light.

Subjects: Meteorology and Climatology.

Reference entries