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COMPUTED FARADAY ROTATION DURING SPORADIC-E PROPAGATION
STANFORD UNIV CA STANFORD ELECTRONICS LABS
Because they exist in thin sheets, sporadic-E layers tend to affect radio waves in a manner which is very similar to the reflection of light waves by a mirror. A question then arises concerning the presence or absence of Faraday rotation of the plane of polarization of the electromagnetic field when it is propagated from ground to ground by means of sporadic-E reflection. This paper presents the results of a comprehensive set of digital computer calculations designed to reveal the number of turns which should theoretically be expected in such circumstances. Since the answers are strongly affected by the ionization density underneath the sporadic-E layer, this D-region ionization was chosen with some care. The answer also depends markedly on whether the radio wave is refracted within a sporadic-E layer or whether it is reflected off the layer by virtue of an abrupt change in the index of refraction. Computed results are given for both of these cases, since the true nature of this mechanism is not presently known. Results show that rotation is greatest at low frequencies, low takeoff angles, and geomagnetic azimuths near O deg, and also that rotation is more marked in the daytime than at night.
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