Sun Dog at High Sun, Cape Cod

Last updated on September 16, 2023

Sun Dog at High Sun, Cape Cod: Exploring Rare Halo Displays

When it comes to atmospheric optics, few phenomena captivate the imagination as much as the elusive sun dog. These enchanting displays of light can be observed under specific conditions, and they often create a breathtaking spectacle in the sky. In this article, we will delve into a particular instance of a sun dog sighting at high sun in Cape Cod, Massachusetts, shedding light on the unique features and rare halo formations associated with this occurrence.

On September 1, 2006, Jim Kirk, an avid photographer, captured a remarkable series of images showcasing halos over Cape Cod. The sun was positioned at an impressive altitude of 52°, casting its rays through thin cirrus clouds. This combination produced an extraordinary halo display that went beyond the conventional 22° distance from the sun. The photograph revealed a sundog situated at the same altitude as the sun, tracing the parhelic circle and extending even further than the bright circumscribed halo.

To understand the formation of sundogs at such high solar altitudes, we must explore the intricate interplay of sunlight with plate crystals in the atmosphere. Sundogs occur when sunlight undergoes multiple internal reflections between the upper and lower basal faces of these ice crystals. At lower altitudes, sundogs are typically observed at an angular distance of 22° from the sun. However, in this instance, the sundog remained aligned with the sun's altitude, defying conventional expectations.

Upon closer examination of Jim Kirk's photograph, one can spot faint arcs extending from the sundog towards the circumscribed halo. These ethereal arcs, known as Parry arcs, are exceptionally rare to witness during high sun conditions. Unlike Lowitz arcs, which are commonly observed in lower sun positions, Parry arcs add an additional layer of mystique to this already captivating phenomenon.

The presence of Parry arcs in this particular halo display highlights the complex interaction between sunlight and plate crystals. These arcs form when sunlight interacts with horizontally oriented, pencil-shaped ice crystals. As light passes through these crystals, it refracts and bends, creating the distinct Parry arcs that appear as extensions of the sundog towards the circumscribed halo.

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In conclusion, the sighting of a sun dog at high sun in Cape Cod, Massachusetts, offers a fascinating glimpse into the world of atmospheric optics. The exceptional altitude of the sun, combined with the presence of thin cirrus clouds, created a rare halo display that defied conventional expectations. The alignment of the sundog with the sun's altitude and the presence of Parry arcs added an extra layer of intrigue to this already captivating phenomenon. Through the lens of Jim Kirk's photographs, we are reminded of the beauty and complexity that exists within our atmosphere, waiting to be discovered and admired.

Cape Cod, Massachusetts Halos imaged by Jim Kirk September 1, 2006. ©Jim Kirk, shown with permission.

The sun is 52° high and thin cirrus produces a spectacular and rare halo display. This image from Jim Kirk's extensive series of photographs shows a sundog far from the conventionally thought of 22° distance from the sun. It remains at the sun's altitude and on the parhelic circle but lies beyond even the bright circumscribed halo.

Sunlight has to internally reflect an even number of times from the upper and lower basal faces of plate crystals to produce sundogs at these high solar altitudes.

Look carefully for faint arcs extending from the sundog towards the circumscribed halo. these are not Lowitz arcs but rare high sun Parry arcs.

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

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