Snake Valley Halo

Last updated on September 16, 2023

Snake Valley Halo: A Spectacular Atmospheric Phenomenon

Have you ever witnessed a mesmerizing halo around the sun that seemed to create a "hole in the sky"? One such captivating spectacle is the Snake Valley Halo. This extraordinary atmospheric optics phenomenon is formed by the interaction of sunlight with hexagonal ice prisms suspended in the atmosphere. Let's delve into the details and explore this fascinating occurrence further.

Understanding the Snake Valley Halo

The Snake Valley Halo is a type of halo that manifests as a 22° ring encircling the sun. Unlike a high-sun circumscribed halo, which appears oval when the solar altitude is around 73°, the Snake Valley Halo maintains a circular shape. One way to distinguish it from other halos is by observing its diffuse and pastel colors, which give it a softer and less vibrant appearance compared to a circumscribed halo.

The "Hole in the Sky" Effect

One of the most captivating aspects of the Snake Valley Halo is its ability to create what is commonly referred to as the "hole in the sky" effect. This effect occurs due to the deviation of rays passing through hexagonal ice prisms, which contribute their glints to the halo. These rays are deviated at a minimum angle of 22°, resulting in a noticeable absence of crystal glints within this region surrounding the sun. Consequently, this area appears darker, creating a distinct "hole" amidst the sky.

The Formation Process

To fully grasp the formation of the Snake Valley Halo, it is essential to understand the role of ice crystals in its creation. These hexagonal ice prisms are typically found in high-altitude cirrus clouds or in the upper layers of the troposphere. When sunlight passes through these ice crystals, it undergoes a process known as refraction. Refraction causes the light to bend, and different wavelengths of light disperse, resulting in the characteristic colors observed in the halo.

A Symphony of Light

The Snake Valley Halo is a captivating display of atmospheric optics that showcases the interplay between sunlight and ice crystals. The hexagonal shape of the ice prisms plays a crucial role in the formation of the halo. As sunlight enters an ice prism, it refracts and undergoes internal reflection within the prism's walls. This internal reflection causes the light to exit the prism at a specific angle, creating a symphony of light that culminates in the beautiful halo we observe.

Optical Phenomena Associated with the Snake Valley Halo

While the Snake Valley Halo is the primary optical phenomenon observed, it often appears alongside other atmospheric wonders. These include:

• Sun Dogs: These are bright spots that appear on either side of the sun, caused by the refraction of sunlight through ice crystals.
• Parhelia: Also known as sundogs, parhelia are bright spots that appear at the same altitude as the sun, forming a "mock sun" on either side.
• Circumzenithal Arcs: These arcs form above the sun and have a vivid display of colors. They are caused by sunlight refracting through horizontal ice crystals.

Capturing the Beauty of the Snake Valley Halo

To truly appreciate the ethereal beauty of the Snake Valley Halo, many photographers and enthusiasts have sought to capture its magnificence. The delicate pastel hues and distinctive ring shape make it an alluring subject for photography. With careful timing and positioning, photographers can capture stunning images that showcase this awe-inspiring atmospheric phenomenon.

Scientific Significance

Beyond its visual appeal, studying the Snake Valley Halo and other atmospheric optics phenomena provides valuable insights into the composition and behavior of our atmosphere. By analyzing these optical occurrences, scientists can gain a deeper understanding of atmospheric conditions, such as ice crystal formations and cloud dynamics. This knowledge contributes to various scientific fields, including meteorology, climatology, and atmospheric physics.

A Reminder of Nature's Wonders

The Snake Valley Halo serves as a captivating reminder of the intricate and awe-inspiring phenomena that occur in our atmosphere. It is a testament to the beauty and complexity of the natural world. So, the next time you find yourself gazing at the sky, keep an eye out for this remarkable halo, and let yourself be enchanted by its ethereal presence.

Conclusion

The Snake Valley Halo is a mesmerizing atmospheric optics phenomenon that creates a circular 22° halo around the sun. Its soft and diffuse colors, coupled with the "hole in the sky" effect, make it a sight to behold. Understanding the interplay between sunlight and ice crystals helps explain its formation. Alongside other optical phenomena such as sun dogs and circumzenithal arcs, the Snake Valley Halo adds a touch of magic to our skies. Whether capturing its beauty through photography or studying its scientific significance, this remarkable halo serves as a reminder of nature's wonders and the mysteries that await us above.

Snake Valley Halo - Imaged by Ken James (Snake Valley Astr. Assn.) at Snake Valley, Victoria, Australia on Jan 9, 2009 when the sun was a summer's 73° high. ©Ken James, shown with permission.

It is a 22� halo rather than a high-sun circumscribed halo because at the solar altitude of 73� the latter would be measurably oval. Another guide is that its colours are diffuse and pastel. Those of the circumscribed halo are slightly sharper and more saturated.

The halo nicely shows the 'hole in the sky' effect. Rays passing through hexagonal ice prisms and contributing their glints to the halo are deviated a minimum of 22�. Many rays are deviated through greater angles but none less. The absence of crystal glints within 22� of the sun makes the sky noticeably darker there - a hole in the sky.

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Reference Atmospheric Optics

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