Twilight arch

(Section 3.2.3.11.2)

In the direction opposite to the Sun, the Earth’s shadow and the twilight arch are sometimes seen. The Earth’s shadow gradually rises above the horizon opposite the Sun after sunset. It appears as a segment of a disc, appearing dark blue−grey and sometimes with a violet tinge. The twilight arch often appears as a rose violet ribbon bordering the upper edge of the shadow. Above this arch, a faint purple or yellow colour is sometimes seen.