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   120� Parhelia 

A 120� parhelion brightens the parhelic circle. Far from the sun, these parhelia arise from multiple reflections inside relatively thick oriented plate crystals.  To the right of the 120� parhelion, the otherwise colourless parhelic circle is very slightly blue ~ the 'blue spot'. Further right around the anthelic point (the point opposite to the sun but at the same altitude), singly oriented columns generate even more exotic halos.    HaloSim simulation centered 150� from a 15� high sun.

120� parhelion ray path through a near horizontal plate crystal.   
Always look carefully for 120� parhelia whenever the ordinary 22� sundogs are very bright.   They are not particularly rare, but when they are diffuse they can sometimes be difficult to distinguish from bright areas of cloud.

The parhelia result from at least two internal reflections. Rays enter the plate crystal top face, internally reflect off two adjacent side faces then leave through the lower face. The horizontal deflection of the ray is always 120� regardless of the angle of incidence of the incoming ray ~ hence the parhelion rather than yet another parhelic circle ray.