18°-halo

18°-Ring 

EE 32

Crystal orientation:

at random

Path of light:

13-25

Occurrence:

very rarely

Pyramidal-Halodisplay with 9°-, 18°-, 22/°-, 24°-halo . 05/28/1999, at 11.11 AM, f=18mm, Höllviken/Southsweden
Photo: © Richard Löwenherz

Description:

An 18°-halo is a white ring of light with a radius of 18° around the sun. In most cases it appears together with other halos caused by pyramid-shaped ice crystals.

Simulation of pyramidal halos.
Grafik: W. Tape; Atmospheric Halos; S. 89; Am. Geophysical Union; 1994

Formation:

18°-halos are caused by randomly orientated pyramid-shaped ice crystals. The path of light can be seen in the diagram above.