A vertical shaft of light extending above a setting or rising sun is called a sun pillar. You could have seen this optical phenomenon if you were looking at the sunset on Jan. 18.
While sun pillars look like vertical beams of light projected above the sun, they are actually a collection of reflections of millions of ice crystals floating in the atmosphere.
This optical feature is caused by the reflection of sunlight off tiny ice crystals in a cloud that is near the horizon. Reflection takes place at the boundary of an object. Flat, six-sided, plate-like ice crystals floating in the atmosphere act like small mirrors, reflecting the sun’s light at their flat surfaces.
When in the right location between you and the sun, the ice crystals act like mirrors and reflect sun light off their surfaces toward your eyes. If the crystals were not there, the sunbeams that they are reflecting would never be seen by you; those beams of light would be traveling far above your head.
On this same day, the snow at times sparkled. As with the sun pillar, flat crystals resting on top of a blanket of snow can act like tiny mirrors, reflecting a portion of the sun’s image toward your eye.
Each “sparkle” is an individual ice crystal reflecting the sun’s image. Whether we see the sparkle depends on the angle formed between where the sun is, where we are looking and the angle at which the snowflake is resting. If all these conditions are right, occasionally as we walk by a field of snow, we’ll see it glitter because of how the sun is being reflected by the different crystals of snow.
