Ionosphere
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Ionosphere
</dt>
The atmospheric
shell characterized by a high ion density. Its base is at about 70 or 80
kilometers and it extends to an indefinite height.
</dd>
The ionosphere is classically subdivided into layers. Each layer,
except the D-layer, is supposedly characterized by a more or less regular
maximum of electron density. The D-layer exists only in the daytime. It is not
strictly a layer at all, since it does not exhibit a peak of electron or ion
density, starting at about 70 to 80 kilometers and merging with the bottom of
the E-layer. The lowest clearly defined layer is the E-layer, occurring
between 100 and 120 kilometers. The F1-layer and F2-layer occur in the general
region between 150 and 300 kilometers, the F2-layer being always present and
having the higher electron density. The existence of a G-layer has been
suggested, but is questionable. The portions of the ionosphere in which these
layers tend to form are known as ionosphere in which these layers tend to form
are known as ionospheric regions, as in D-region, E-region, F-region,
G-region. Sudden increases in ionization are referred to as sporadic, as in
sporadic E or sporadic D. The above assumption that the ionosphere is
stratified in the vertical into discrete layers is currently under serious
question. Some evidence supports a belief that ion clouds are the basic
elements of the ionosphere. Other investigations appear to reveal the
ionosphere as a generally ionized region characterized by more or less random
fluctuations of electron density. [[/a>|/a>
]]
References
This article is based on NASA's Dictionary of Technical Terms for Aerospace Use
