Infralateral arc (EE22)

The infralateral arcs are also referred to as the lower lateral contact arcs on the large ring. Their shape depends on the solar height. As the sun's height increases, the contact points move downward along the ring to the 46° ring . Consequently, the infralateral arcs form a common arc. At a solar height of 68°, the arc touches the 46° ring directly below the sun. When the sun rises even higher, the vertex of the arc is a few degrees below the 46° ring. The infralateral arc can match the circumzenithal arc in brightness and colorfulness. At solar altitudes above 58°, the infralateral arc touches the circumhorizontal arc. When the sun is low, the arcs run mostly below the horizon. They are therefore usually observed in ice fog, from mountains or from aircraft. In the halo key, EE22A denotes the left and EE22B the right infralateral arc.

The infralateral arc forms in floating column crystals, with light entering at a vertical base face and exiting at a prism face. These are the same columns that also produce the supralateral arc and the tangent arcs. It therefore often appears together with them.