EE 31

Crystal orientation:
at random
Path of light:
very rarely
Picture 9° halo
The picture shows a 9°-halo. There is a 22° and 24°-halo too.
Photo: Wolfgang Hinz, Chemnitz, 04/03/1998


A 9°-halo is a white ring of light with a radius of 9° around the sun. It often appears together with other halos caused by pyramid-shaped ice crystals. But occasions are few in which there are enough pyramid—shaped crystals to generate a halo. As the ring is situated rather near to the sun it is difficult to recognize it. Furthermore it can easily be taken for a corona.

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


A 9°-halo is caused by randomly orientated pyramid-shaped ice crystals. It is generated by light entering a base face and leaving an adjacent pyramidal face.