Subsuns & Pillars
|Subsuns and lower pillars are both reflections from myriad horizontal plate crystals. Each crystal glints sun rays from its upper or lower hexagonal face.
Well aligned - by aerodynamic drag forces - crystals have these faces horizontal to better than one degree. That produces a subsun, an almost circular solar reflection. Large less well oriented crystals can wobble several degrees and a sun pillar results.
Crystal tilt is the only real distinction between the two.