The tangents arcs of the 22° halo appear as two separate arcs when
the sun is low and as a single circumscribed halo when the sun is high.
They are tangent to the 22° halo at its highest and lowest points.
They can appear as brightening of the 22° halo. The shape of the
circumscribed halo depends very much on the altitude of the sun. When
the sun is low all that can be seen is that the upper tangential bow
is bent back in a downward direction. At higher altitudes of the sun
an almost elliptical figure can appear.