skystos

Skystos are a class of transient, luminous filaments observed in the upper atmosphere. They appear as slender, ribbon-like structures that are often translucent and pale blue-green, suspended at altitudes in the upper mesosphere and lower thermosphere. Skystos typically persist for a few seconds to several minutes and can drift with prevailing winds and electric fields.

The term skystos was coined in the late 2030s by researchers studying high-altitude optical phenomena. The name combines the common reference to the sky with a suffix used in plasma-structure nomenclature, signaling their filamentary, ionized nature.

Formation and characteristics are still an active area of research. Skystos are thought to result from interactions between atmospheric ions and neutral particles under strong electric fields, modulated by gravity waves and turbulence in the upper atmosphere. They exhibit intermittent brightness and a thread-like morphology, sometimes forming intertwined networks. Spectral observations typically reveal a broad emission compatible with airglow and ionized species present at high altitudes.

Distribution and observations show that skystos have been reported most often in polar and subpolar regions during periods of geomagnetic activity or impressive atmospheric disturbances, though isolated appearances have been documented elsewhere with sensitive instrumentation. They are usually detected through imaging systems, spectrometers, and, in some cases, lidar.

Scientific significance lies in their potential to illuminate coupling between atmospheric layers, upper-atmosphere electricity, and wave dynamics. Studying skystos can contribute to understanding mesoscale processes and the limits of optical observations in near-space environments. See also: sprite, blue jet, elve, noctilucent cloud, airglow.