A lower sun pillar, or subsun, is formed when sunlight reflects off tiny hexagonal ice crystals. It extends vertically below the real sun. At first, the subsun appeared as a dazzling ball of glittering diamond dust suspended magically in midair. Later in the day, the effect intensified until it became a solid pillar of heavenly light, as bright as the real sun.
In the painting The Annunciation by Henry Ossawa Tanner, I find it interesting how he depicts the archangel Gabriel as a glowing pillar of light. I wonder if he had a similar natural phenomenon in mind when he painted it?