asenduskulus

Asenduskulus is a proposed atmospheric optical phenomenon described as a diffuse, multicolored glow observed near the western horizon during twilight. Reported appearances include soft, arching bands or veils in tones of magenta, cyan, and gold, with durations ranging from several seconds to a few minutes. Observers typically report the effect shortly after sunset when residual twilight interacts with upper atmospheric layers.

Etymology and status: The term was coined by a group of field researchers in the mid-2010s to classify a twilight glow that did not fit established categories. It remains a provisional designation pending peer-reviewed confirmation and reproducible observations. Some accounts emphasize variability in color, shape, and intensity across different viewing conditions.

Mechanisms and interpretation: Explanations center on light-scattering and reflection processes in thin clouds, aerosols, and atmospheric layers such as cirrus or noctilucent-like clouds. Humidity gradients, particle composition, and the spectral distribution of sunset sunlight are considered contributing factors. Alternative hypotheses suggest transient luminescent processes in trace atmospheric ions or a misinterpretation of known twilight phenomena (for example, diffuse airglow or distant halos). The relative rarity and locality of reports complicate definitive modeling.

Occurrence and significance: Sightings have been limited and are predominantly reported in coastal temperate regions with persistent hazes or thin cloud decks. There is no broad consensus on its prevalence or mechanism, and some researchers view asenduskulus as a potential variant of established twilight optics rather than a distinct phenomenon. It remains of interest to atmospheric scientists studying twilight illumination and aerosol-cloud interactions.

See also: atmospheric optics, noctilucent clouds, twilight halos.