Icy Pyramids Sculpt Oddball Halos


The upper patch of dull color in this photo taken last week from Duluth is a circumzenithal arc touching part of a larger 46-degree halo. The inner concentric rings around the sun are a rare halo phenomenon caused by pyramid-shaped ice crystals in high cirrostratus clouds. Photo: Bob King

Last Wednesday as the sun dropped in the west, it was surrounded by a remarkable series of halos I’d never before seen. Most common halos are caused by light refracted or bent by microscopic, six-sided ice crystals that look like cut up pencils. Light enters one side of the crystal and is bent at a 22-degree angle as it exits the other side. All the millions of crystals together create a ring around the sun with a radius of 22 degrees.


This is the cropped and enhanced version of the halo pictured above. The sun is ringed by 9, 18 and 22 degree halos, a couple of which show color along their edges. Because pyramid ice crystals have many different faces at a variety of angles to one another, they can create multiple odd-dimension halos. Photo: Bob King

This halo was different. I first noticed a colorful patch, called a circumzenithal arc, well above the main halo. You’ll see in the photo that light continues on either side of the arc to form part of the larger, rarer 46-degree halo. What really caught my eye however were the several nested halos within the space between the sun and the normal 22-degree halo.

After a search through books and online sources, I discovered that these odd, concentric halos were caused by pyramidal ice crystals. In the contrast-enhanced picture you can count at least three of them near the sun.

What amazes me is that you can see hundreds of halos in your lifetime and still not see them all. The constant interplay of light and ice has surprises in store for both daytime and nighttime skywatchers. For more on this unusual phenomenon, you can visit this website.

I’m not the only one that’s been busy with their camera. We’ve also received some really nice photos from our readers in the past week. Here they are for you to enjoy. Thank you Lyle and Andrew for sending them.


The fair city of Duluth reflects on a calm Lake Superior last Thursday night. Photo credit: Lyle Anderson


The International Space Station cuts a path of light through the sky from Duluth’s Park Point Sunday morning. The little wiggle at the far left end of the trail was caused by camera movement, possibly the wind. At upper right, you can see the W of Cassiopeia. Photo credit: Lyle Anderson


The photo of lightning bugs last week inspired photographer Andrew Kirk of Bishop, Calif. to send this picture of colorful water trails. "Drops of water flung from a rushing mountain stream catch sunlight as they spin and distort. A single drop may rotate and reflect numerous times during its flight and even refract mini-rainbows back to the camera," Kirk writes.
Photo credit: Andrew Kirk

6 Responses

  1. Andrew Kirk

    Wow, I saw your halo photos on Spaceweather and thought they were amazing…without even noticing your name. Now I KNOW they incredible!!!!

  2. astrobob

    Hi D.M — I’d go one step further and say they’re rare any time of year at least compared to the 22-degree variety. This was my first one ever though I bet I’ve passed a few by without noticing. I’ll be paying closer attention now that I know what to look for.

  3. D. Anderson

    Bob,

    Your photos caught my attention because a physicist friend of mine has been telling me about these high clouds and that they portend a sharp cooling ahead. For what it’s worth, here is what he said when I shared your article with him:

    Obviously, I’m observing the same thing. I call the high cirrus, “wakefield”, because they have a pattern that’s reminiscent of water flow aft of a boat hull in motion in the shape of solitons. Another example is seen in laser wakefield acceleration.

    For several days last week they disappeared and then today they reappeared. There were two levels, one at about 6 kilomters and the other at 10. The higher have the new development.

    I claim these new development higher cirrus follow a pattern now existent for 3 years that represent beginning evidence of a major reversal of the last 30 years of weather. For the refraction indicated in those photos ice crystals have to be super-cooled and tumbled which shows the cirrus are stratospheric and therefore are intercepting UV photons not absorbed by ozone.

    UV has been high for 15 years and this has caused much higher surface temperatures. The reason for high UV is low ozone density. What mediates ozone? Energetic catalyst. Maybe cosmic rays and solar wind in some reinforcing combo that changes the rate free O oxidizes O3 into O2, or availability of O. Specifically, O3 is quasi stable so that some high speed ion, proton, through its resulting muon shower which brings down its activation energy threshold, increases the O3 —> O2 reaction.

    What’s it mean? Cold surface temperatures, cold surface waters, and that means no hurricanes and horrendous winters.

  4. astrobob

    D.A., Fascinating thoughts on the subject. I wonder if his hypothesis could be true. It certainly points in the opposite direction from the global warming forecasts. We’ll have to wait and see. Thanks for sending.

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