165:" or "parhelia". (Often on these occasions, the sun is also surrounded by a luminous ring or halo, the angle between the sun and the halo (with the observer at the angle’s vertex) measuring 22°.) On rare occasions, faint arcs extend upwards or downwards from these sun dogs. These arcs extending from the sun dogs are "Lowitz arcs". As many as three distinct arcs may extend from the sun dogs. The short arc that first inclines towards the sun and then extends downward is called the "lower Lowitz arc". A longer second arc may also extend downward from the sun dog but then curve under the sun, perhaps joining the other sun dog; this is the "middle Lowitz arc" or "circular Lowitz arc". Finally, a third arc may extend upwards from the sun dog; this is the "upper Lowitz arc". In his diagram of 1790, Lowitz recorded only a lower Lowitz arc.
52:
195:
hypothetical Lowitz arc can be predicted and compared against photographs of actual arcs. As a result of such simulations, the traditional explanation of Lowitz arcs has been found to have some shortcomings. Specifically, simulations assuming that only perfectly hexagonal, rotating plates produce Lowitz arcs, predict the wrong intensities for the arcs. More accurate simulations were obtained by assuming that the plates were almost horizontal, or that the ice crystals had a more rhombic shape or were hexagonal columns that were oriented horizontally.
20:
191:
the ice plates rotate, plates throughout an arc are—at some time during each rotation—oriented to refract sunlight to the observer. A hexagonal plate has three long diagonals about which it can rotate, but rotation around only one of the axes causes the lower Lowitz arc. The other Lowitz arcs—the middle and upper arcs—are caused by sunlight passing through the two other pairs of faces of the hexagonal ice plate.
621:
183:(1812 - 1910) proposed that lower Lowitz arcs were produced as sun dogs are; that is, by sunlight refracting through hexagonal ice crystals. However, in the case of sun dogs, the columnar crystals are oriented vertically, whereas in the case of Lowitz arcs, Galle proposed, the crystals oscillated about their vertical axes.
325:(6): 322–330; from page 328: "The arcs of Lowitz are of special theoretical interest on account of their extreme rarity with questionable authenticity … " As late as 1994, Walter Tape stated: "And in spite of subsequent reports of Lowitz arcs , there seem to be no photographs of them." (Walter Tape, ed.,
55:
Lowitz's diagram of solar halos (1790). The Sun (labeled αβa) lies within the two overlapping circles near the bottom of the image. Sun dogs (labeled bx and cy) lie to the Sun's left and right. The "Lowitz arcs" (labeled xi and yk) descend at an acute angle from the sun dogs and intersect the circles
194:
However, since circa 1990, photographs of what are clearly Lowitz arcs have become available for study. Furthermore, numerical ray-tracing software allows Lowitz arcs to be simulated by computers, so that, from hypotheses about the shape and orientation of ice crystals, the shape and intensity of a
186:
Charles
Sheldon Hastings (1848 - 1932), an American physicist who specialized in optics, suggested in 1901 that Lowitz arcs were due to hexagonal plates of ice, which oscillated around a horizontal axis in the plane of the plate as the plate fell, similar to the fluttering of a falling leaf. Later,
190:
According to
Hastings, sunlight enters one of the faces on the edge of the plate, is refracted, propagates through the ice crystal, and then exits through another face on the edge of the plate, which is at 60° to the first face, refracts again as it exits, and finally reaches the observer. Because
152:
However, some scientists (not unreasonably) doubted the existence of the phenomenon: the phenomenon rarely occurs; and since Lowitz arcs were little known, people who witnessed them didn’t always recognize them; furthermore, until the advent of small, inexpensive digital cameras, witnesses rarely
153:
had, at hand, cameras to record them, and even if they did have cameras, the cameras weren’t always sensitive enough to record the faint Lowitz arcs. Only since circa 1990 have photographs of what are clearly Lowitz arcs become available for study and analysis.
78:
6. Ces deux derniers parhélies qui se trouvoient à quelque distance des intersections du grand cercle horizontal par les deux couronnes qui entourent le soleil, renvoyoient d'abord des deux cotés de parties d'arc très courtes colorées
116: : 6. These last two parhelia which were at some distance from the intersections of the great horizontal circle by the two coronas which surrounded the sun, sent, in the first place, from the two sides very short colored arcs
148:
Lowitz formally reported the phenomenon to the St. Petersburg
Academy of Sciences on October 18, 1790, including a detailed illustration of what he had witnessed. The illustration included what are now called “lower Lowitz arcs”.
487:
The "long diagonals" of a hexagonal plate pass from the junction of two faces on the edge of the plate, through the plate's center, and then through the junction of two faces on the edge of the plate on the opposite side of the
537:(accompanied by a 22° halo, an upper tangent arc, and a suncave Parry arc), and a computer simulation of the display, and the refractions through a columnar hexagonal ice crystal which are believed to create the arc.
64:(or Lovits) (1757 - 1804), a German-born Russian apothecary and experimental chemist. On the morning of June 18, 1790 in St. Petersburg, Russia, Lowitz witnessed a spectacular display of solar
161:
Sometimes, when the sun is low in the sky, there are luminous spots to the left and right of the sun and at the same elevation as the sun. These luminous spots are called "
176:(bending) through ice crystals. However, there still remains some dispute about the shape and orientation of the ice crystals that produce Lowitz arcs.
756:
723:
Arbeitskreis
Meteore e.V. : Spectacular display of halos, etc., on November 27, 2010 in the Sudelfeld in the Bavarian Alps (in German)
315:
534:
731:
51:
453:
573:
736:
722:
751:
65:
36:
447:
701:
Halo
Observation Project : database of observations of rare halos, etc., with photos (from 1990s to 2006)
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408:
592:
338:
See page 252 of: M. Riikonen, L. Cowley, M. Schroeder, M. Pekkola, T. Ă–hman, and C. Hinz (September 2007)
180:
187:
in 1920, he proposed that the plates rotate, rather than merely oscillate, around their long diagonals.
569:
329:, Antarctic Research Series, vol. 64 (Washington, D. C.: American Geophysical Union, 1994), page 98.)
61:
275:(Description of a remarkable atmospheric phenomenon, observed at St. Petersburg on June 18, 1790),
68:. Among his observations, he noted arcs descending from the sun dogs and extending below the sun:
563:
255:
87:
dont la direction s'inclinoit au dessous du soleil jusqu'aux deux demi-arcs de cercle intérieurs
32:
551:
366:
647:
James R. Mueller, Robert G. Greenler, and A. James
Mallmann (August 1, 1979) "Arcs of Lowitz,"
475:
412:
290:
272:
222:
603:
620:, Antarctic Research Series, vol. 64 (Washington, D. C.: American Geophysical Union, 1994).
404:
285:
An
English translation of (most of) Lowitz's article appears in: Charles Sheldon Hastings,
73:
339:
19:
705:
Arbeitskreis
Meteore e.V. (German group devoted to observations of atmospheric optics):
217:
304:
Atmospheric Optics : Lowitz's sketch of the solar halos and arcs of June 18, 1790
249:
745:
23:
Lowly visible lines going up and down from the side sun are most likely Lowitz's arcs
124:
whose direction inclined below the sun as far as the two interior semicircular arcs
638:
140:, directed away from the sun and included in the circumference of the great circle
737:
Photos of halo phenomena at Mount
Geigelstein in the Bavarian Alps (Oct. 15, 2005)
457:
National
Academy of Sciences of the United States of America Biographical Memoirs
273:"Déscription d'un météore remarquable, observé à St. Pétersbourg le 18 Juin 1790"
198:
Hence the exact mechanism by which Lowitz arcs are produced, remains unresolved.
95:. En second lieu ils Ă©toient pourvues des queues longues, claires & blanches
700:
591:, 2nd ed. (New York, New York: McGraw-Hill, 1929); Lowitz arcs are discussed on
169:
624:(in the absence of photographic evidence), Tape regards Lowitz arcs as merely
173:
691:
303:
686:
625:
384:
361:
235:
103:, opposées au soleil & renfermées dans la circonference du grand cercle
712:
717:
427:
Frederick E. Beach (June 1, 1932) "Charles Sheldon Hastings: 1848-1932,"
162:
692:
Atmospheric Optics : HaloSim3 (software for simulating halos, etc.)
552:"Mémoire sur les halos et les phénomènes optiques qui les accompagnent"
40:
582:
pages 360-380: 47. Nebensonne, Halo von 22° und Lowitz' schiefe Bögen.
395:
G. Galle (1840) "Ueber Höfe und Nebensonnen" (On halos and sun dogs),
371:
246:
For brief biographies of Johann Tobias Lowitz (1757 - 1804), see:
50:
35:
that occurs in the atmosphere; specifically, it is a rare type of
554:(Memoir on halos and the optical phenomena that accompany them),
172:
and sun dogs, Lowitz arcs are believed to be caused by sunlight
287:
Light: A consideration of the more familiar phenomena of optics
271:
Lowitz, Johann Tobias (presented: 1790 ; published: 1794)
732:
Ice Crystal Halos : a collection of photos of halos, etc.
533:
Halo researcher Marko Riikonen's Web site displays a photo of
132:. In the second place, they had long tails, bright and white
580:, 2nd ed. (Vienna, Austria: Wilhelm BraumĂĽller, 1922). See:
454:"Biographical Memoir of Charles Sheldon Hastings 1848-1932,"
236:
Atmospheric Optics: Computer generated images of Lowitz arcs
277:
Nova Acta Academiae Scientiarum Imperialis Petropolitanae
602:(Cambridge, England: Cambridge University Press, 1980);
39:
that forms a luminous arc which extends inwards from a
635:(Washington, D. C.: American Geophysical Union, 2006).
411:, and Table 1; for Galle's theory of Lowitz arcs, see
289:( New York, New York: Charles Scribner's Sons, 1901),
282:: 384-388; on page 386, the Lowitz arcs are described.
250:
Encyclopedia.com : Lovits (Lowitz), Johann Tobias
438:
Frank Schlesinger (1932) "Charles Sheldon Hastings,"
43:(parhelion) and may continue above or below the sun.
367:
Halo Reports. blog spot. com : 46° contact arcs
679:
Atmospheric Optics (Website devoted to halos, etc.)
584:(47. Sun dogs, 22° halo and Lowitz's oblique bows.)
713:Arbeitskreis Meteore e.V. : Upper Lowitz arc
362:Atmospheric Optics : Lowitz arcs -- Gallery
564:pages 47-49: "§ X. -- Arcs obliques de Lowitz."
372:Atmospheric Optics : Reflected Lowitz arcs
669:(Helsinki, Finland: Ursa, 2011) -- in Finnish.
424:Obituary notices of Charles Sheldon Hastings:
358:Photographs of Lowitz arcs are available at:
157:The phenomenon and hypotheses about its cause
8:
633:Atmospheric Halos and the Search for Angle X
446:(3) : 149 - 155. Available on-line at:
718:Arbeitskreis Meteore e.V. : Lowitz arc
649:Journal of the Optical Society of America
604:Lowitz arcs are discussed on pages 44-47
314:See, for example: Hastings, C.S. (1920)
18:
658:R.A.R. (Ronald Alfred Ranson) Tricker,
556:Journal de l'Ecole royale polytechnique
207:
687:Atmospheric Optics : Lowitz arcs
662:(New York, New York: Elsevier, 1970).
660:Introduction to Meteorological Optics
385:Atmospheric Optics : Lowitz arcs
7:
223:Merriam-Webster : Arc of Lowitz
448:SAO / NASA Astrophysics Data System
218:Dictionary.com : Arc of Lowitz
609:Walter Tape (researcher of halos):
254:German Knowledge (XXG)'s article:
14:
515:Riikonen et al. (2007), page 252.
667:Halot. Jääkidepilvien valoilmiöt
631:Walter Tape and Jarmo Moilanen,
179:In 1840, the German astronomer
60:The phenomenon is named after
1:
757:Atmospheric optical phenomena
397:Annalen der Physik und Chemie
600:Rainbows, Halos, and Glories
316:"A general theory of halos,"
214:Definitions of Lowitz arcs:
587:William Jackson Humphreys,
429:American Journal of Science
773:
506:Hastings (1920), page 329.
497:Hastings (1920), page 329.
566:(Lowitz's oblique arcs).
550:Auguste Bravais (1847)
452:Horace S. Uhler (1938)
524:Riikonen et al. (2007)
319:Monthly Weather Review
181:Johann Gottfried Galle
146:
110:
57:
56:that surround the Sun.
24:
655:(8) : 1103-1106.
639:Walter Tape's website
578:Meteorologische Optik
440:Astrophysical Journal
111:
70:
54:
22:
562: : 1-270. See:
256:Johann Tobias Lowitz
62:Johann Tobias Lowitz
570:Josef Maria Pernter
535:an upper Lowitz arc
616:Walter Tape, ed.,
589:Physics of the Air
58:
33:optical phenomenon
25:
16:Optical phenomenon
752:Optical phenomena
618:Atmospheric Halos
598:Robert Greenler,
574:Felix Maria Exner
474:Hastings (1901),
435:(138): 485 - 489.
327:Atmospheric Halos
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665:Marko Riikonen,
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72:Original (in
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114:Translation
746:Categories
626:Parry arcs
622:On page 98
463:: 273-291.
202:References
174:refracting
29:Lowitz arc
168:Like the
476:page 219
403: :
163:sun dogs
409:241-291
343:Weather
47:History
41:sun dog
488:plate.
136:&
128:&
120:&
99:&
91:&
83:&
74:French
31:is an
268:See:
66:halos
572:and
405:1-31
142:afhg
105:afbg
138:y η
134:x ζ
130:dke
126:die
101:y η
97:x ζ
93:dke
89:die
76:):
748::
653:69
651:,
576:,
560:18
558:,
461:20
459:,
444:76
442:,
433:23
407:,
401:49
399:,
347:62
345:,
323:48
321:,
122:yk
118:xi
85:yk
81:xi
27:A
628:.
606:.
595:.
478:.
415:.
280:8
144:.
107:.
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