Circumscribed Halos

Complex Ice‐crystal Halo Phenomena: Sky Archaeology

“…(8) There also appears o n the photograph a short, indistinct sun pillar passing through the sun. It agrees with the shape produced by reflection from the sides of oriented pencil crystals(Greenler et al 1972) although we have not added it t o the simulation ofFig. 3.…”

“…1) passing through crystals tumbling with random orientation produce the 22" halo. (Greenler and Mallmann 1972. ) (2) Rays A, E, and F for random crystal orientations would produce the 46" halo.…”

“…Rays C, for crystals with horizontal axes and all degrees of rotation around those axes, produce the upper tangent arc to the 22" halo. (Greenler and Mallmann 1972. ) (4) If there is an additional degree of orientation so that a pair of long side faces are constrained to be horizontal (f3") the upper suncave Parry arc shown in the simulation, arching over the top of the upper tangent arc, is produced by rays C. (Greenler et al 1977.…”

Formation of atmospheric halos and applicability of geometric optics for calculating single-scattering properties of hexagonal ice crystals: Impacts of aspect ratio and ice crystal size

“…Several studies have simulated circumscribed halos and other optical phenomena by calculating ray paths that depend on the relative positions between the Sun and ice crystals (or orientations of ice crystals) and on the sunlight path through the faces of crystals [7][8][9][10][11][12][13][14][15][16][17]. For example, the 221 and 461 halos are caused by the minimum deviation of sunlight due to the refraction through a 601 prism formed by alternate side faces, and a 901 prism formed by the side and basal faces of hexagonal crystals, respectively.…”

The World of Light

“…Other effects, such as 'sun dogs' ('false suns' appearing either horizontally on one or both sides of the Sun or vertically above the Sun) and 'sun pillars', vertical shafts of light often seen directly above the Sun at sunset, are similarly caused by ice crystals. These ice crystal effects have recently been treated in some detail (Greenler and Mallmann, 1972;Greenler et al, 1972). Other phenomena are observed under certain conditions of mist or dew, such as 'glories' (halos seen in the mist around the shadow of one's own head) and 'heiligenschein', an aureole of light around the shadow of one's head on dewy grass.…”