OPOD - Lower Pillar

Last updated on September 16, 2023

OPOD - Lower Pillar: A Glimpse into the Enchanting World of Atmospheric Optics

Have you ever marveled at the stunning phenomena that occur in the Earth's atmosphere? One such captivating display is the lower sun pillar, a reminder of the enchanting beauty of winter. Lower sun pillars, also known as sun pillars, are optical illusions that occur when sunlight reflects off ice crystals in the atmosphere, creating a vertical column of light that appears to extend below the sun. In this article, we will delve into the fascinating world of lower sun pillars and explore the intricacies of their formation.

The Discovery of a Lower Sun Pillar

On December 24, 2010, Doug Short, an avid observer of atmospheric phenomena, had a serendipitous encounter with a lower sun pillar in Alaska. Despite the frigid temperature of -22 Celsius (-8 Fahrenheit), Doug was captivated by the glimmering spectacle in the sky. The sun, positioned 2.7 degrees above the horizon, cast its radiant glow upon a multitude of diamond dust particles suspended in the air. As Doug positioned himself to capture this ephemeral moment, he noticed the glittering reflections from the lower sun pillar, extending all the way to just a few feet in front of him. Upon closer examination of his photographs, he discovered that some of the closest ice crystals exhibited large, bright, and almost circular reflections, likely originating from unfocused diamond dust crystals.

Unveiling the Magic: The Composition of Sun Pillars

The images captured by Doug Short provide a vivid reminder that sun pillars and other ice halos are composed of millions of individual ice crystals, each contributing its own glint to the spectacle. These crystals can vary in proximity to the observer, with some being far away and others in close proximity. The circular shapes observed in some of Doug's glints are likely a result of the very close and unfocused diamond dust crystals, which create a mesmerizing effect.

The Role of Crystal Shape and Alignment

While most sun pillars are produced by reflections from plate-shaped ice crystals, other ice halos require well-aligned crystals to be observed. The plate-shaped crystals responsible for sun pillars drift in air currents with their large hexagonal faces predominantly horizontal. However, these crystals can tilt away from their mean horizontal position, and the degree of tilting directly influences the length of the sun pillar. In contrast, other ice halos, such as sundogs and circumzenithal arcs, require precise alignment of the ice crystals to create their distinct formations.

The Camera's Perspective: Capturing Glints of Beauty

As Doug Short's photographs demonstrate, the air surrounding a lower sun pillar is teeming with glinting ice crystals. However, the camera lens can only capture those glints that happen to be directed towards it, resulting in the appearance of the sun pillar. This selective perspective highlights the importance of capturing the right moment to fully appreciate and document these awe-inspiring atmospheric phenomena.

Imperfect Beauty: Sun Pillar Crystals

Sun pillar crystals, unlike the perfectly shaped examples often illustrated in textbooks, tend to be larger and more imperfect. These imperfections cause the crystals to appear wobbly when reflecting sunlight, adding an element of dynamic movement to the lower sun pillar. It is these imperfections that contribute to the unique and captivating nature of these optical illusions.

Exploring Further

If you find yourself captivated by the enchanting world of atmospheric optics, there is a wealth of knowledge and resources available for further exploration. Websites such as Atmospheric Optics offer a treasure trove of information on various atmospheric phenomena, including sun pillars, halos, rainbows, and more. By delving deeper into this captivating field, you can expand your understanding and appreciation of the wonders that unfold in the sky above us.

In conclusion, the lower sun pillar is a breathtaking display of nature's artistic prowess. Its formation relies on the interplay between sunlight, ice crystals, and atmospheric conditions. As we gaze upon these mesmerizing optical illusions, let us marvel at the intricate beauty that surrounds us and continue to explore the captivating world of atmospheric optics.

Lower Sun Pillar

A reminder of winter. Doug Short in Alaska imaged this lower sun pillar. ©Doug Short, shown with permission

"While out and about on December 24, 2010, I spotted a lower sun pillar at 14:50 in the afternoon. It was -22 Celsius (-8 Fahrenheit) that day. The sun was 2.7 degrees above the horizon and there was a fair bit of diamond dust in the air. When I positioned myself for a photo I noticed the glitter from the lower sun pillar all the way to just a few feet in front of my position. When I took a close look at the photos I was intrigued that the reflections from some of the closest ice crystals were quite large and bright and almost circular. You can see those at the bottom of the elongated vertical photo."

The images remind us that sun pillars and all ice halos are composed of the glints of millions of individual crystals. Some crystals may be far away, others very close. The circular shapes of some of Doug's glints are probably from very close and thus unfocussed diamond dust crystals.

Most sun pillars are produced by sun reflections from plate shaped crystals. These drift in air currents with their large hexagonal faces more or less horizontal. They tilt away from the mean horizontal position and the larger the tilts the longer is the sun pillar. In contrast, other ice halos require well aligned crystals to be seen.

The air was full of glinting crystals. The camera sees only those - the sun pillar - that happened to glint towards the lens.

Sun pillar crystals tend to be large and imperfect - hence wobbly - rather than the perfect habits illustrated below.

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Reference Atmospheric Optics

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