| main | ongoing | archive | private |
- Afterglow - a broad arch of whitish or pinkish sunlight in the twilight sky, consisting of the bright segment and the purple light.
- Airglow - a faint emission of light by a planetary atmosphere. In the case of Earth's atmosphere, this optical phenomenon causes the night sky never to be completely dark, even after the effects of starlight and diffused sunlight from the far side are removed. This phenomenon originates with self-illuminated gases and has no relationship with Earth's magnetism or sunspot activity.
- Alexander's band - the dark region between the two bows of a double rainbow.
- Alpenglow - a horizontal reddish glow near the horizon opposite to the Sun when the solar disk is just below the horizon.
- Anthelion - a rare optical phenomenon of the halo family. It appears on the parhelic circle opposite to the Sun as a faint white spot, not unlike a sundog, and may be crossed by an X-shaped pair of diffuse arcs.
- Anticrepuscular rays - meteorological optical phenomena similar to crepuscular rays, but appear opposite the Sun in the sky. Anticrepuscular rays are essentially parallel, but appear to converge toward the antisolar point, the vanishing point, due to a visual illusion from linear perspective.
- Aurora - also commonly known as the northern lights (aurora borealis) or southern lights (aurora australis), is a natural light display in Earth's sky, predominantly seen in high-latitude regions (around the Arctic and Antarctic). Auroras display dynamic patterns of brilliant lights that appear as curtains, rays, spirals, or dynamic flickers covering the entire sky.
- Auroral light (northern and southern lights, aurora borealis and aurora australis)
- Belt of Venus - an atmospheric phenomenon visible shortly before sunrise or after sunset, during civil twilight. It is a pinkish glow that surrounds the observer, extending roughly 10–20° above the horizon. It appears opposite to the afterglow, which it also reflects.
- Brocken Spectre - also called Brocken bow, mountain spectre, or spectre of the Brocken is the magnified (and apparently enormous) shadow of an observer cast in mid-air upon any type of cloud opposite a strong light source. The figure's head can be surrounded by a bright area called Heiligenschein, or halo-like rings of rainbow-coloured light forming a glory, which appear opposite the Sun's direction when uniformly-sized water droplets in clouds refract and backscatter sunlight.
- Circumhorizontal arc - an optical phenomenon that belongs to the family of ice halos formed by the refraction of sunlight or moonlight in plate-shaped ice crystals suspended in the atmosphere, typically in actual cirrus or cirrostratus clouds. In its full form, the arc has the appearance of a large, brightly spectrum-coloured band (red being the topmost colour) running parallel to the horizon, located far below the Sun or Moon.
- Circumzenithal arc - also called the circumzenith arc (CZA), upside-down rainbow, and the Bravais arc, 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 colourful members of the halo family. Its colours, 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.
- Cloud iridescence - a colourful optical phenomenon that occurs in a cloud and appears in the general proximity of the Sun or Moon. The colours resemble those seen in soap bubbles and oil on a water surface. It is a type of photometeor. This fairly common phenomenon is most often observed in altocumulus, cirrocumulus, lenticular, and cirrus clouds.
- Crepuscular rays - are sunbeams that originate when the Sun appears to be just above or below a layer of clouds, during the twilight period.
- Earth's shadow - the shadow that Earth itself casts through its atmosphere and into outer space, toward the antisolar point. During the twilight period (both early dusk and late dawn), the shadow's visible fringe – sometimes called the dark segment or twilight wedge – appears as a dark and diffuse band just above the horizon, most distinct when the sky is clear.
- Earthquake lights - also known as earthquake lightning or earthquake flash is a luminous optical phenomenon that appears in the sky at or near areas of tectonic stress, seismic activity, or volcanic eruptions. There is no broad consensus as to the causes of the phenomenon (or phenomena) involved. The phenomenon differs from disruptions to electrical grids – such as arcing power lines – which can produce bright flashes as a result of ground shaking or hazardous weather conditions.
- Glories - an optical phenomenon, resembling an iconic saint's halo around the shadow of the observer's head, caused by sunlight or (more rarely) moonlight interacting with the tiny water droplets that comprise mist or clouds. The glory consists of one or more concentric, successively dimmer rings, each of which is red on the outside and bluish towards the centre. Due to its appearance, the phenomenon is sometimes mistaken for a circular rainbow, but the latter has a much larger diameter and is caused by different physical processes.
- Green flash - meteorological optical phenomena that sometimes occur transiently around the moment of sunset or sunrise. When the conditions are right, a distinct green spot is briefly visible above the Sun's upper limb; the green appearance usually lasts for no more than two seconds. Rarely, the green flash can resemble a green ray shooting up from the sunset or sunrise point.
- Halos, of Sun or Moon - an optical phenomenon produced by light (typically from the Sun or Moon) interacting with ice crystals suspended in the atmosphere. Halos can have many forms, ranging from colored or white rings to arcs and spots in the sky. Many of these appear near the Sun or Moon, but others occur elsewhere or even in the opposite part of the sky.
- Haze - an atmospheric phenomenon in which dust, smoke, and other dry particulates suspended in air obscure visibility and the clarity of the sky.
- Heiligenschein or halo effect, partly caused by the opposition effect
- Iceblink - a white light seen near the horizon, especially on the underside of low clouds, resulting from reflection of light off an ice field immediately beyond. The iceblink was used by both the Inuit and explorers looking for the Northwest Passage to help them navigate safely.
- Light pillar - an atmospheric optical phenomenon in which a vertical beam of light appears to extend above and/or below a light source. The effect is created by the reflection of light from tiny ice crystals that are suspended in the atmosphere or that comprise high-altitude clouds (e.g. cirrostratus or cirrus clouds). If the light comes from the Sun (usually when it is near or even below the horizon), the phenomenon is called a sun pillar or solar pillar. Light pillars can also be caused by the Moon or terrestrial sources, such as streetlights and erupting volcanoes.
- Lightning - a natural phenomenon formed by electrostatic discharges through the atmosphere between two electrically charged regions, either both in the atmosphere or one in the atmosphere and one on the ground, temporarily neutralizing these in a near-instantaneous release of an average of between 200 megajoules and 7 gigajoules of energy, depending on the type.
- Mirages - a naturally occurring optical phenomenon in which light rays bend via refraction to produce a displaced image of distant objects or the sky.
- Monochrome rainbow - an optical and meteorological phenomenon and a rare variation of the more commonly seen multicoloured rainbow. Its formation process is identical to that of a normal rainbow (namely the reflection/refraction of light in water droplets), the difference being that a monochrome rainbow requires the sun to be close to the horizon; i.e., near sunrise or sunset. The low angle of the sun results in a longer distance for its light to travel through the atmosphere, causing shorter wavelengths of light, such as blue, green and yellow, to be scattered and leaving primarily red.
- Moon dog - an atmospheric optical phenomenon that consists of a bright spot to one or both sides of the Moon. They are exactly analogous to sun dogs.
- Moonbow - also known as a moon rainbow or lunar rainbow, is a rainbow produced by moonlight rather than direct sunlight. Other than the difference in the light source, its formation is the same as for a solar rainbow: It is caused by the refraction of light in many water droplets, such as a rain shower or a waterfall, and is always positioned in the opposite part of the sky from the Moon relative to the observer.
- Nacreous cloud/Polar stratospheric cloud - clouds in the winter polar stratosphere at altitudes of 15,000–25,000 m (49,000–82,000 ft). They are best observed during civil twilight, when the Sun is between 1 and 6 degrees below the horizon, as well as in winter and in more northerly latitudes. One main type of PSC is made up mostly of supercooled droplets of water and nitric acid and is implicated in the formation of ozone holes. The other main type consists only of ice crystals which are not harmful.
- Rainbow - an optical phenomenon caused by refraction, internal reflection and dispersion of light in water droplets resulting in a continuous spectrum of light appearing in the sky. The rainbow takes the form of a multicoloured circular arc.
- Rayleigh scattering - a predominantly elastic scattering of light, or other electromagnetic radiation, by particles with a size much smaller than the wavelength of the radiation. For light frequencies well below the resonance frequency of the scattering medium (normal dispersion regime), the amount of scattering is inversely proportional to the fourth power of the wavelength, e.g., a blue color is scattered much more than a red color as light propagates through air.
- Subsun - an optical phenomenon that appears as a glowing spot visible within clouds or mist when observed from above. The subsun appears directly below the actual Sun, and is caused by sunlight reflecting off of numerous tiny ice crystals suspended in the atmosphere. As such, the effect belongs to the family of halos. The region of ice crystals acts as a large mirror, creating a virtual image of the Sun appearing below the horizon, analogous to the Sun's reflection in a body of water.
- Sun dog - 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.
- Tangent arc - 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.
- Tyndall effect - light scattering by particles in a colloid such as a very fine suspension (a sol). Also known as Tyndall scattering, it is similar to Rayleigh scattering, in that the intensity of the scattered light is inversely proportional to the fourth power of the wavelength, so blue light is scattered much more strongly than red light.
- Upper-atmospheric lightning, including red sprites, Blue jets, and ELVES
- Water sky - a phenomenon that is closely related to iceblink. It forms in regions with large areas of ice and low-lying clouds and so is limited mostly to the extreme northern and southern sections of earth, in Antarctica and in the Arctic.
mar 10 2024 ∞
apr 13 2024 +
apr 13 2024 +