Scintillation
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Scintillation
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1. Generic term for rapid variations in apparent position, brightness, or
color of a distant luminous object viewed through the atmosphere.
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If the object lies outside the earth's atmosphere, as in the case of
stars and planets, the phenomenon is termed astronomical scintillation; if the
luminous source lies within the atmosphere, the phenomenon is termed
terrestrial scintillation. As one of the three principal factors governing
astronomical seeing, scintillation is defined as variations in luminance
only. It is clearly established that almost all scintillation effects are
caused by anomalous refraction occurring in rather small parcels or strata of
air, schlieren, whose temperatures and hence densities differ slightly from
those of their surroundings. Normal wind motions transporting such schlieren
across the observer's line of sight produce the irregular fluctuations
characteristic of scintillation. Scintillation effects are always much more
pronounced near the horizon than near the zenith. Parcels of the order of only
centimeters to decimeters are believed to produce most of the scintillatory
irregularities in the atmosphere.
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2. A flash of light produced in a phosphor by an
ionizing
event. See scintillation counter. 3. On a radar display, a rapid apparent
displacement of the target from its
mean position. Also called target glint or wander.
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This includes but is not limited to shift of effective reflection point
on the target. [[/a>|/a>
]]
References
This article is based on NASA's Dictionary of Technical Terms for Aerospace Use
