Auroras

1. When solar wind disturbs the magnetosphere in high-latitudes, skyborne light displays of varying color and complexity can appear (aurora). A localized form form can also arise, faint and elongated (picket fence aurora).

Coronae

1. Coronae form from diffraction in comparatively large ice crystals. Diffracted sunlight and moonlight can create concentric, pastel-colored rings with a bright central aureole. This can also take place filtered through airborne pollen, causing a vertical elongation.

Ghost Lights

1. Atmospheric ghost lights refer to various unexplained light phenomena. This can include flickering lines or fires (kitsunebi), glowing discharges (St. Elmo’s Fire), fuzzy, hovering, disc-shaped lights (min min light)s, and various luminescent or flaming balls: orbs (onibi), globes (shiranui), fireballs (tenka), and lanterns (will-o’-wisp).

Glories

1. Sunlight or moonlight refraction in water droplets can also cause concentric, successively dimmer rings around the shadow of an observer’s head. Similarly, glories can arise as brocken spectre, magnified and enormous-appearing shadows of an observer’s body projected upon clouds opposite the Sun, with a glory of colored light. Finally, dew can act as comparable lenses, enabling bright outlines around an observer’s shadow.

Glows

1. Atmospheric glows can appear in many forms, including distortions like the short period in morning or evening twilight where sunlight takes a more blue shade (blue hour) and the short period of daytime after sunrise or before sunset where sunlight takes a more red shade (golden hour).

2. This can also manifest as sunset afterglows, and pinkish bands in the sky during civil twilight (belt of venus), as well as false sunrises or false sunsets, which near mountains and clouds can appear as alpenglow long after sunset or long before sunrise.

3. Various dry particulates can obscure the daytime sky (haze), whereas faint emissions of light by the planetary atmosphere (airglow) ensure the night sky never completely darkens.

Ice Crystal Halos (Frequent)

1. Sunlight interacting with ice crystals that act as prisms and mirrors suspended in the atmosphere can create halos in the sky, ranging from colored or white rings, to arcs and spots, sometimes near Sun or Moon, and potentially circumscribed by further ovals of light (circumscribed halo).

2. Halos can appear as bright spots: a glowing spot below the sun when seen from above (subsun), or bright spots appearing on an arc of light aside Sun or Moon (sun dog, moon dog).

3. Halos can appear as lines: vertical beams of light (light pillars), horizontal white lines sometimes featuring parhelia (parhelic circle), or even as a horizontal rainbow band below the Sun or Moon and parallel to the horizon (circumhorizontal arc)

4. Halos can appear as arcs: an upper or lower arc tangent to a halo (tangent arc), or even a rainbow arc above the Sun (circumzenithal arc).

Ice Crystal Halos (Infrequent)

1. Halos can appear in even rarer forms, such as bright spots on parhelic circle (120* parhelion) or a faint white spot or x-shape opposite the Sun on top of parhelic circle (anthelion), or a halo below the horizon (subparhelic circle).

2. They can also appear as rare circles or rings: a complete faint circle (kern arc), or a ring around the Sun (46* halo).

3. They can also appear as rare diffuse disks: a halo around the sun after volcanic eruption (bishop’s ring), or a solar or lunar elliptical halo.

4. Many rarer halos appear as arcs, such as an upside-down rainbow arc (infralateral arc), or a luminous arc extending inward from a sun dog (lowitz arc), or a complex halo with upper and lower tangent arcs (parry arc), or a halo curving upward from the horizon and touching an arc above the point directly opposite the Sun from the observer (subhelic arc), or a rainbow-colored band in a wide arc above the Sun and seemingly encircling it (supralateral arc).

Iridescent Clouds

1. Instead of halos, smaller ice crystals create iridescence, a colorful optical phenomenon, pastel or vivid, in a cloud in general proximity to the Sun or Moon. This can appear as a brightening thunderhead crown followed by an aurora-like emanation (crown flash), as iridescent mountain clouds, as an upper atmosphere phenomena during astronomical twilight (noctilucent clouds), or as a winter polar stratospheric phenomena during civil twilight (polar stratospheric clouds).

Mirages

1. Atmospheric optical illusions come in several forms. Just after sunset or right before sunrise, green flashes can manifest as very brief green spots above the upper rim of the Sun’s disk.

2. Atmospheric temperature gradients can refract light to the point of an inferior mirage, a vibrating, towering, or stooping illusion under the real object, typically appearing as blue sky upside-down on the ground in an unstable projection like water. By contrast, superior mirages appear above the true object, mostly in polar regions, and have more stability.

3. The most complex mirages arise as fata morgana, a narrow band right above the horizon which drastically distorts a base object, sometimes rapidly, into stacks of inverted and upright images, with alternating compressed and stretched zones.

Rainbows

1. Reflection, refraction, and dispersion of light in water droplets can result in multicolored circular arcs in the sky: rainbows. These can sometimes have second concentric arcs (double rainbow), or diverge as twinned rainbows as the base splits, sometimes even forming triple rainbows with tertiary arcs. Similarly, on water surfaces, two complementary mirror bows can appear above and below the horizon, and rarely even more complex reflected rainbows formations can arise too. One or several faint and narrow bands can border a rainbow’s edge, creating concentric arcs of subdued pastel hues (supernumerary rainbows).

2. Rainbow-like phenomena can also occur in dew (dewbow), in fog (fogbow), or through moonlight rather than direct sunlight (moonbow).

3. Rainbows can have more or less completion. During sunrise or sunset, deep-red monochrome rainbows can form. And at elevation, observers can sometimes witness full-circle rainbows.

Rays & Shadows

1. Rays of sunlight can appear to radiate through clouds as beams of light (crepuscular rays), sometimes opposite the Sun in the sky (anticrepuscular rays).

2. Atmospheric shadows can take many forms. The opposite of a crepuscular ray, a cloud shadow, appears when a cloud casts its shadow across the sky. Conversely, planets can also cast their own shadow onto their atmosphere, appearing as a dark and diffuse band low above the horizon during twilight.

3. Via perspective effects, downward mountain shadows appear where an observer at a summit perceives an apparent triangular shadow projected on the sky, and upward mountain shadows appear projected upward onto a lower level translucent cloud or mist. Finally, mountain shadows can appear as 2D ridge shadow effects on an opposite valley wall combined with 3D shadows cast onto the air itself by the pinnacle (corrugated mountain shadow).

Reflections

1. Various waterborne reflections can take place, including white light on the underside of clouds, near icefields, seen near the horizon (iceblink), or dark spots appearing beneath low-lying clouds over the sea in polar latitudes (water sky).

2. Moonlight and sunlight can also create bright reflections on water (moonglade, sun glitter).

Shines

1. Faint shines in the night can appear around the antisolar point (countershine), or as a triangular glow extending from the Sun’s direction along the zodiac (zodiacal light).