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148:. The reflection can be either external (e.g. without the light passing through the crystal) which contributes to the parhelic circle near the Sun, or internal (one or more reflections inside the crystal) which creates much of the circle away from the Sun. Because an increasing number of reflections makes
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The intensity distribution of the parhelic circle is largely dominated by 1-3-2 and 1-3-8-2 rays (cf. the nomenclature by W. Tape, i.e. 1 denotes the top hexagonal face, 2 the bottom face, and 3-8 enumerate the side faces in counter-clockwise fashion. A ray is notated by the sequence in which it
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being the material's index of refraction (not the
Bravais index of refraction for inclined rays). However, many more features give a structure to the intensity pattern of the parhelic circle. Among the features of the parhelic circle are the Liljequist parhelia, the 90° parhelia (likely
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115:. If complete, it stretches all around the sky, but more commonly it only appears in sections. If the halo occurs due to light from the Moon rather than the Sun, it is known as a
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290:{\displaystyle \theta _{{\mathfrak {1}}{\mathfrak {3}}{\mathfrak {2}}}=2\arcsin \left(n\cos \left(\arcsin \left(1/n\right)\right)/\cos \left(e\right)\right)}
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571:"Intensity distribution of the parhelic circle and embedded parhelia at zero solar elevation: theory and experiments"
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encounters the prism faces). The former ray-path is responsible for the blue spot halo which occurs at an azimuth.
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A halo display observed over the South Pole. Featured in the photo are several distinct phenomena: A
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Sillanpää, M.; Moilanen, J.; Riikonen, M.; Pekkola, M. (2001). "Blue spot on the parhelic circle".
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unobservable), the second order 90° parhelia (unobservable), the 22° parhelia and more.
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Parhelic circles form as beams of sunlight are reflected by vertical or almost vertical
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130:. While parhelic circles are generally white in colour because they are produced by
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are always aligned to the parhelic circle (but not always to the 22° halo).
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appearing as a horizontal white line on the same altitude as the
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asymmetric some colour separation occurs away from the Sun.
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134:, they can however show a bluish or greenish tone near the
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A nearly complete paraselenic circle, along with a partial
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Even fractions of parhelic circles are less common than
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138:and be reddish or deep violet along the fringes.
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324:Artificial parhelic circles can be realized by
23:A crisp parhelic circle (horizontal line) over
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328:using, for instance, spinning crystals.
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419:"Paraselenae & Paraselenic circle"
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16:Type of halo, an optical phenomenon
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569:Borchardt, S.; Selmke, M. (2015).
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455:simulation of a parhelic circle.)
627:Atmospheric Optics – Ice Halos
1:
642:Atmospheric optical phenomena
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373:. 1980-12-21. Archived from
338:Upper and lower tangent arcs
85:Piszkéstető Mountain Station
7:
536:American Journal of Physics
467:"Parhelic Circle Formation"
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10:
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91:(Hungary), February 2023.
451:(including an excellent
79:. Photo is taken by the
53:(bright spots), and an
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111:, or occasionally the
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29:Photo: John Bortniak,
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45:(horizontal line), a
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595:10.1364/AO.54.006608
509:10.1364/ao.40.005275
469:. Atmospheric Optics
421:. Atmospheric Optics
399:. Atmospheric Optics
367:"A magnificent halo"
348:Liljequist parhelion
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166:
59:Photo: Cindy McFee,
587:2015ApOpt..54.6608B
548:2015AmJPh..83..751S
530:Selmke, M. (2015).
501:2001ApOpt..40.5275S
442:. www.paraselene.de
89:Konkoly Observatory
532:"Artificial Halos"
343:Circumzenithal arc
326:experimental means
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117:paraselenic circle
105:optical phenomenon
93:
65:
49:(circle) with two
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25:South Pole Station
581:(22): 6608–6615.
556:10.1119/1.4923458
495:(30): 5275–5279.
440:"Parhelic Circle"
397:"Parhelic Circle"
313:{\displaystyle n}
55:upper tangent arc
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75:and the eastern
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43:parhelic circle
33:, January 1979.
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621:External links
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575:Applied Optics
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542:(9): 751–760.
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489:Applied Optics
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471:. Retrieved
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444:. Retrieved
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423:. Retrieved
417:Les Cowley.
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401:. Retrieved
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379:. Retrieved
375:the original
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146:ice crystals
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473:2007-04-15
446:2009-02-01
425:2021-10-07
403:2007-04-15
381:2007-04-14
354:References
150:refraction
132:reflection
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171:θ
143:hexagonal
128:22° halos
636:Category
611:39382489
603:26368071
517:18364808
332:See also
154:Sun dogs
124:sun dogs
77:moon dog
47:22° halo
583:Bibcode
544:Bibcode
497:Bibcode
453:HaloSim
83:of the
51:sundogs
609:
601:
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229:arcsin
204:arcsin
607:S2CID
300:with
103:, an
599:PMID
513:PMID
371:NOAA
126:and
113:Moon
101:halo
61:NOAA
31:NOAA
591:doi
552:doi
505:doi
266:cos
218:cos
109:Sun
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