Montana Halos - OPOD

Montana Halos - A Mesmerizing Atmospheric Phenomenon

Montana, known for its picturesque landscapes, is not only a treat for nature enthusiasts but also a haven for atmospheric optics enthusiasts. The state's wide open spaces and pristine skies create the perfect conditions for the formation of a stunning array of ice halos. These ethereal displays, captured by photographer Marc Roston in Whitefish, Montana, showcase the mesmerizing beauty of the Montana Halos.

Exploring the Enigmatic Montana Halos

The Montana Halos exhibit a variety of captivating optical phenomena that occur due to the interaction of sunlight with ice crystals suspended in the atmosphere. Let's delve into the intricacies of these enchanting displays:

  1. The 22° Halo: The most prominent feature of the Montana Halos is the 22° halo, encircling the sun. This halo forms when sunlight refracts and reflects within hexagonal ice crystals, creating a circular band of light at an angle of 22° from the sun.

  2. Parhelic Circle and Helic Arcs: Crossing the sun, we find the parhelic circle, a faint band of light resulting from sunlight reflecting off horizontally oriented ice crystals. Additionally, rarer helic arcs radiate from the sun, adding an extra touch of magic to the display.

  3. Tangent Arcs: At the base of the 22° halo, a lower tangent arc blazes brightly. This arc is formed by sunlight passing through horizontally oriented ice crystals. Joining this lower tangent arc is the infrequently glimpsed lower Wegener arc, extending downwards from a sundog. These arcs add a unique element to the overall spectacle.

  4. Supralateral and Infralateral Arcs: Twice as far from the sun as the 22° halo, colorful supralateral and infralateral arcs grace the sky. These arcs are created by sunlight interacting with hexagonal ice crystals oriented in a specific manner.

  5. Parry Arcs: The Montana Halos also feature Parry arcs, such as the Upper Suncave Parry and helic arcs radiating from the sun. These arcs result from the presence of Parry-oriented ice crystals, which contribute to the intricate beauty of the display.

  6. Completing the Display: Wobbly plate crystals complete the Montana Halos, forming the parhelion, subparhelion, and subsun. These elements, along with the faint join between the sundog and subdog, add an extra layer of complexity to the phenomenon.

Unveiling the Secrets with HaloSim Ray Tracing

To gain a deeper understanding of the Montana Halos, researchers utilize advanced techniques like HaloSim ray tracing. By simulating the interaction of light with ice crystals, scientists can unravel the complex mechanisms behind these atmospheric optics phenomena. Here's what they have discovered:

  • Randomly oriented hexagonal columns are used to generate the 22° halo, capturing its distinct circular shape.
  • Singly oriented columns contribute to the intense upper and lower tangent arcs, while horizontal columns are responsible for the supralateral, infralateral, and Wegener arcs.
  • Parry-oriented columns produce the Upper Suncave Parry and helic arcs radiating from the sun, adding to the overall allure of the display.
  • The presence of wobbly plate crystals completes the Montana Halos, creating the parhelion, subparhelion, and subsun.

Witnessing the Montana Halos

If you find yourself in Montana on a day when diamond dust fills the air and the sun shines brightly, keep an eye on the sky. The Montana Halos may grace you with their presence, offering a truly awe-inspiring spectacle of atmospheric optics.

Remember to be patient and observant, as these displays are relatively rare and require specific atmospheric conditions to occur. When they do appear, take a moment to marvel at the intricate dance of light and ice crystals that creates these captivating phenomena.

A Reminder from the Past

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The Montana Halos are a testament to the breathtaking wonders of nature and the remarkable interplay between light and ice crystals in the atmosphere. Let yourself be enchanted by the ethereal beauty of these atmospheric optics phenomena, and immerse yourself in the captivating world of Montana's halos.

A Parry arc glints in diamond dust above an upper tangent arc

Montana Halos ~ Above and below horizon ice halos captured by Marc Roston at Whitefish, Montana.

A 22� halo circles the sun. The sun is crossed by a parhelic circle and rarer helic arcs. A lower tangent arc blazes at the base of the 22� halo. From it stretches an infrequently glimpsed lower Wegener arc. Colour streams downwards from a sundog to meet a fainter subparhelion.

All images ©Marc Roston, shown with permission

Twice as far from the sun as the 22 halo are colourful supralateral and infralateral arcs.

A HaloSim ray tracing of the display. It used randomly oriented hexagonal columns to generate the 22 degree halo.

Singly oriented columns made the intense upper and lower tangent arcs. In reality the UTA was less bright, probably because there were fewer diamond dust crystals along the upwards line of sight.. The same horizontal columns gave the supralateral, infralateral and Wegener arcs.

A few Parry oriented columns produced the Upper suncave Parry and the helic arcs radiating from the sun.

Wobbly plate crystals completed the display to make the parhelion, subparhelion and subsun. The 'join' between the sundog and subdog comes out faint in ray tracings.

Note: this article has been automatically converted from the old site and may not appear as intended. You can find the original article here.

Reference Atmospheric Optics

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  • "Montana Halos - OPOD". Atmospheric Optics. Accessed on March 28, 2024. https://atoptics.co.uk/blog/montana-halos-opod/.

  • "Montana Halos - OPOD". Atmospheric Optics, https://atoptics.co.uk/blog/montana-halos-opod/. Accessed 28 March, 2024

  • Montana Halos - OPOD. Atmospheric Optics. Retrieved from https://atoptics.co.uk/blog/montana-halos-opod/.