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Parhelic Circle
A parhelic circle is a type of halo, an optical phenomenon appearing as a horizontal white line on the same altitude as the sun, or occasionally the Moon. 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 paraselenic circle. Even fractions of parhelic circles are less common than sun dogs and 22° halos. While parhelic circles are generally white in colour because they are produced by reflection, they can however show a bluish or greenish tone near the 120° parhelia and be reddish or deep violet along the fringes. (including an excellent HaloSim simulation of a parhelic circle.) Parhelic circles form as beams of sunlight are reflected by vertical or almost vertical hexagonal ice crystals. 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 Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Halo And Sun Dog - NOAA
Halo, halos or haloes usually refer to: * Halo (optical phenomenon) * Halo (religious iconography), a ring of light around the image of a head HALO, halo, halos or haloes may also refer to: Arts and entertainment Video games * Halo (franchise), ''Halo'' (franchise), a video game franchise ** ''Halo: Combat Evolved'', the first game in the series ** Halo Array, fictional megastructures and superweapons in the franchise Film and television * Halo (1996 film), ''Halo'' (1996 film), a drama film made in India * Halo (2007 cancelled film), ''Halo'' (2007 cancelled film), a cancelled movie based on ''Halo'' video game franchise * Halo (TV series), ''Halo'' (TV series), a 2022 TV series based on the ''Halo'' video game franchise * Nickelodeon HALO Awards, annual American television special (2008–2018) Comics * Comics in the Halo (franchise)#Comics, ''Halo'' franchise * Halo (DC Comics), a fictional superheroine * the title character of ''The Ballad of Halo Jones'', a science-fiction ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Circumzenithal Arc
The circumzenithal arc, also called the circumzenith arc (CZA), upside-down rainbow, and the Bravais arc,"Mémoire sur les halos et les phénomènes optiques qui les accompagnent", J. de l' École Royale Polytechnique 31(18), 1-270, A. Bravais, 1847 is an optical phenomenon similar in appearance to a rainbow, but belonging to the family of halos arising from refraction of sunlight through ice crystals, generally in cirrus or cirrostratus clouds, rather than from raindrops. The arc is located at a considerable distance (approximately 46°) above the observed Sun and at most forms a quarter of a circle centered on the zenith. It has been called "a smile in the sky", its first impression being that of an upside-down rainbow. The CZA is one of the brightest and most colorful members of the halo family. Its colors, ranging from violet on top to red at the bottom, are purer than those of a rainbow because there is much less overlap in their formation. The intensity distribution along ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Upper And Lower Tangent Arcs
Tangent arcs are a type of halo, an atmospheric optical phenomenon, which appears above and below the observed Sun or Moon, tangent to the 22° halo. To produce these arcs, rod-shaped hexagonal ice crystals need to have their long axis aligned horizontally. Description Upper arc The shape of an upper tangent arc varies with the elevation of the Sun; while the Sun is low (less than 29–32°) it appears as an arc over the observed Sun forming a sharp angle. As the Sun is seen to rise above the Earth's horizon, the curved wings of the arc lower towards the 22° halo while gradually becoming longer. As the Sun rises over 29–32°, the upper tangent arc unites with the lower tangent arc to form the circumscribed halo. Lower arc The lower tangent arc is rarely observable, appearing under and tangent to a 22° halo centred on the Sun. Just like upper tangent arcs, the shape of a lower arc is dependent on the altitude of the Sun. As the Sun is observed slipping over Earth's h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sun Dog
A sun dog (or sundog) or mock sun, also called a parhelion (plural parhelia) in meteorology, is an atmospheric optical phenomenon that consists of a bright spot to one or both sides of the Sun. Two sun dogs often flank the Sun within a 22° halo. The sun dog is a member of the family of halos caused by the refraction of sunlight by ice crystals in the atmosphere. Sun dogs typically appear as a pair of subtly colored patches of light, around 22° to the left and right of the Sun, and at the same altitude above the horizon as the Sun. They can be seen anywhere in the world during any season, but are not always obvious or bright. Sun dogs are best seen and most conspicuous when the Sun is near the horizon. Formation and characteristics Sun dogs are commonly caused by the refraction and scattering of light from horizontally oriented plate-shaped hexagonal ice crystals either suspended in high and cold cirrus or cirrostratus clouds, or drifting in freezing moist air at low ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Refraction
In physics, refraction is the redirection of a wave as it passes from one medium to another. The redirection can be caused by the wave's change in speed or by a change in the medium. Refraction of light is the most commonly observed phenomenon, but other waves such as sound waves and water waves also experience refraction. How much a wave is refracted is determined by the change in wave speed and the initial direction of wave propagation relative to the direction of change in speed. For light, refraction follows Snell's law, which states that, for a given pair of media, the ratio of the sines of the angle of incidence ''θ1'' and angle of refraction ''θ2'' is equal to the ratio of phase velocities (''v''1 / ''v''2) in the two media, or equivalently, to the refractive indices (''n''2 / ''n''1) of the two media. :\frac =\frac=\frac Optical prisms and lenses use refraction to redirect light, as does the human eye. The refractive index of materials varies with the wavelengt ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ice Crystal
Ice crystals are solid ice exhibiting atomic ordering on various length scales and include hexagonal columns, hexagonal plates, dendritic crystals, and diamond dust. Formation The hugely symmetric shapes are due to depositional growth, namely, direct deposition of water vapor onto the ice crystal. Depending on environmental temperature and humidity, ice crystals can develop from the initial hexagonal prism into numerous symmetric shapes. Possible shapes for ice crystals are columns, needles, plates and dendrites. If the crystal migrates into regions with different environmental conditions, the growth pattern may change, and the final crystal may show mixed patterns. Ice crystals tend to fall with their major axis aligned along the horizontal, and are thus visible in polarimetric weather radar signatures with enhanced (positive) differential reflectivity values. Electrification of ice crystals can induce alignments different from the horizontal. Electrified ice crystals are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hexagon
In geometry, a hexagon (from Ancient Greek, Greek , , meaning "six", and , , meaning "corner, angle") is a six-sided polygon. The total of the internal angles of any simple polygon, simple (non-self-intersecting) hexagon is 720°. Regular hexagon A ''regular polygon, regular hexagon'' has Schläfli symbol and can also be constructed as a Truncation (geometry), truncated equilateral triangle, t, which alternates two types of edges. A regular hexagon is defined as a hexagon that is both equilateral polygon, equilateral and equiangular polygon, equiangular. It is bicentric polygon, bicentric, meaning that it is both cyclic polygon, cyclic (has a circumscribed circle) and tangential polygon, tangential (has an inscribed circle). The common length of the sides equals the radius of the circumscribed circle or circumcircle, which equals \tfrac times the apothem (radius of the inscribed figure, inscribed circle). All internal angles are 120 degree (angle), degrees. A regular hexago ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
120° Parhelion
A 120° parhelion (plural: 120° parhelia) is a relatively rare halo, an optical phenomenon occasionally appearing along with very bright sun dogs (also called parhelia) when ice crystal-saturated cirrus clouds fill the atmosphere. The 120° parhelia are named for appearing in pair on the parhelic circle ±120° from the sun. (including a HaloSim simulation.) When visible, 120° parhelia appear as white-bluish bright spots on the white parhelic circle and are the product of at least two interior reflections in the hexagonal ice crystals. Their colour together with them being rather obscure can make observing them difficult as they tend to fuse with the clouds in the sky. See also * Liljequist parhelion A Liljequist parhelion is a rare Halo (optical phenomenon), halo, an optical phenomenon in the form of a brightened spot on the parhelic circle approximately 150–160° from the sun; i.e., between the position of the 120° parhelion and the anthel ... * Subhelic arc Refere ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Reflection (physics)
Reflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves. The ''law of reflection'' says that for specular reflection (for example at a mirror) the angle at which the wave is incident on the surface equals the angle at which it is reflected. In acoustics, reflection causes echoes and is used in sonar. In geology, it is important in the study of seismic waves. Reflection is observed with surface waves in bodies of water. Reflection is observed with many types of electromagnetic wave, besides visible light. Reflection of Very high frequency, VHF and higher frequencies is important for radio transmission and for radar. Even hard X-rays and gamma rays can be reflected at shallow angles with special "grazing" mirrors. Reflection of light Reflection of light is either ''Specular reflection, specular'' (mi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
22° Halo
A 22° halo is an atmospheric optical phenomenon that consists of a halo with an apparent radius of approximately 22° around the Sun or Moon. When visible around the Moon, it is also known as a moon ring or winter halo. It forms as sunlight or moonlight is refracted by millions of hexagonal ice crystals suspended in the atmosphere. Its radius is roughly the length of an outstretched hand at arm's length. Formation Even though it is one of the most common types of halo, the exact shape and orientation of the ice crystals responsible for the 22° halo are the topic of debate. Hexagonal, randomly oriented columns are usually put forward as the most likely candidate, but this explanation presents problems, such as the fact that the aerodynamic properties of such crystals leads them to be oriented horizontally rather than randomly. Alternative explanations include the involvement of clusters of bullet-shaped ice columns. As light passes through the 60° apex angle of the hexa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
