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https://hdl.handle.net/2142/25634
Description
Title
Midlatitude sporadic-E layers
Author(s)
Miller, Kent Louis
Issue Date
1977
Doctoral Committee Chair(s)
Smith, L.G.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
midlatitude sporadic-E layers
ionosodes
incoherent-scatter radar
Gravity Wave
Language
en
Abstract
The starting point of this investigation is the partially transparent
echo from midlatitude sporadic-E layers as recorded by ionosondes; this is
the range of frequencies between the blanketing frequency and the maximum
frequency. One interpretation is that it is a partial reflection at the
steep gradients of electron density which characterize the vertical profile
of the layers as recorded in rocket flights. The theory of reflection at
gradients is developed and evaluated in the case of five layers. It is
found that this mechanism is not sufficient to explain the phenomenon. An
alternative explanation is that the midlatitude sporadic-E layers are not
uniform in the horizontal plane but contain localized regions of high electron
density. This is investigated using data obtained by incoherent-scatter
radar and is found to provide a satisfactory explanation.
The main features of mid latitude sporadic-E layers are consistent with
the convergence of metallic ions as described by the wind-shear theory
applied to gravity waves and tides. The interference of gravity waves with
other gravity waves and tides can be recognized in the altitudes of
occurrence and the structure of the layers. The small-scale horizontal
irregularities are attributed in some cases to critical level effects and
in others to fluid instabilities. The convergence of a meteor trail can,
under some circumstances, account for localized enhancement of the electron
density in the layer.
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