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Menopausal Mother Nature

News about Climate Change and our Planet


Parhelic circle and halo over Alberta, Canada

The sun to one side, with a 22-degree halo around it, and a 2nd arc, the parhelic circle, extending from the halo.
View at EarthSky Community Photos. | Parhelic circle and 22-degree halo captured August 1, 2021 by Gord Hurlburt. He caught the image in Kananaskis Country, a recreation area to the west of Calgary, Alberta, Canada, in the foothills and front ranges of the Canadian Rockies.

Parhelic circle and halo

Gord Hurlburt captured this remarkable image on August 1, 2021, while hiking down from Burstall – Piggy Plus Col in Kananaskis, Alberta, Canada. You can see the sun on the far right of the image. Around it is a solar halo, known as a 22-degree halo, caused by ice crystals in the upper air. Angling out from the main halo is a 2nd ring. Gord said both the halo and the 2nd ring disappeared after a few minutes. He wrote:

Can you possibly tell me what the 2nd ring is and what might have caused it?

Gord, for all questions related to sky optics, we visit Les Cowley’s great website Atmospheric Optics. The ring around the sun is easy enough. These common halos, 22-degree halo, are caused by ice crystals in the air. In your posting, you mentioned parhelia, aka sundogs. I’m not seeing the sundogs in this image, but, sure enough, the 2nd arc looks as if it’s cutting across the 22-degree halo just at the spot where a sundog might be.

And, sure enough, Les Cowley has a diagram (below) that explains this configuration too. He calls the 2nd arc a parhelic circle. It’s also caused by ice crystals in the air.

Diagram of sun with halos and enlarged, labeled ice crystals.
In this diagram, the sun is surrounded by a 22-degree halo and flanked by parhelia, aka sundogs. Notice the parhelic circle cutting through the sundogs and extending beyond them. Sky optics guru Les Cowley wrote that the parhelic circle: “… sometimes encircles the whole sky at the same altitude as the sun.” Image via Cowley’s Atmospheric Optics.

Bottom line: A photo from an EarthSky community member showing portions of a 22-degree halo and a parhelic circle.


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