Monday, 10 Dec 2018

The story of an incredible sky scene in New Hampshire

There were all kinds of optical phenomena at Franconia Notch in New Hampshire on Sunday. (Steve LeBaron) Mother Nature surely liked that, because she put five rings on it! C & # 39; was the surreal scene Saturday morning at Franconia Notch in New Hampshire. Steve LeBaron of the New Hampshire Department of Transportation's Highway Design Office captured the stunning skies atop Cannon Mountain while skiing. The dazzling fire of LeBaron actually includes seven atmospheric phenomena – some are common, others quite rare. Temperatures below freezing point and high altitude humidity combined to produce a layer of ice crystals in the sky. This alone is not terribly unusual. But in this case, the crystals were mainly shaped like hexagonal columns. They are most often formed at temperatures below 20 degrees. The sunlight that enters the crystalline prisms slows down and splits into colored components. As it leaves the prism, the rays are refracted – or bent – by about 22 degrees. The result? A multicolored group around the sun. In addition, the ice crystals must be misdirected, their randomness allowing the formation of the entire circle of colors. However, unlike rainbows, halos are centered on the sun. Rainbows are anchored around the point of the sky opposite the sun and are wider – 42 degrees.
(Steve LeBaron, adapted by Matthew Cappucci) While refraction is the main actor of halos, reflection is responsible for what is called the parhelic circle. A parhelic circle always develops at the same height in the sky as the sun. It looks like a monochromatic hula-hoop piercing the sun itself. Hexagonal ice crystals are once again an integral part of the process. The different parts of a parhelic circle are filled with orders of different reflections. Near the sun, it is an external reflection, which means that sunlight bounces off the outer wall of an ice crystal and goes elsewhere. Further, the sunlight enters the ice crystal, hitting the wall from the inside before exiting through another face. On occasion, up to five internal reflections can occur, illuminating the halo parts farthest away from the sun. Since refraction does not really play a role, white light is not separated – and does not break down into its assortment of bright shades. Where the
Parhelic circle and 22-degree arc intersect, spots of light called sogs form. This is due to hexagonal prisms parked horizontally; on either side of the sun, the refracted colors are directed directly to the observer. The blue light is refracted more significantly, and the inner edge resulting from the sundog is tinged with red. Parade arches are particularly rare. William Edward Parry attended the show for the first time on April 8, 1820 during a naval quest to find the Northwest Passage. Parry arches involve exceptionally complex ray paths and require specific crystal alignment. This is a similar story for the upper tangent arc. Even more wacky, they flatten as the day progresses, flirting with each other before merging. They are particularly dramatic early in the morning, with the characteristic "v" shape, as shown in LeBaron's photo. Upper and lower tangent arcs appear only near sunrise or sunset. If the sun exceeds 29 degrees above the horizon, the two arches join to form a "circumscribed halo". When the sun rises too high, the two overlaps overlap completely. LeBaron's photo also highlights two other phenomena of the sky. A ray of light called a solar pillar stretches from the sun. Meanwhile, low clouds at the horizon alternately project shadows across the landscape, called twilight rays. The next time you see a ribbon of colors around the sun, try to understand what is happening up there!

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