RECIPROCITY AND NONRECIPROCITY WITH MAGNETOIONIC RAYS

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Abstract
Although the reciprocity theorem of electromagnetism is not generally true when magnetoionic media are present, there can be reciprocity in certain special cases for a radio-communication link. Here the problem is investigated when the approximations of ray theory are valid, where the term "ray theory" is used in a very general sense. For a solution of the electromagnetic equations consisting of rays with a single magnetoionic component, there is a vector W which has zero divergence and is in the same direction as the ray. It can be used to get expressions for the received signals at two stations for transmission in either direction, and these apply for signals consisting of any number of rays. From them it is possible to show when there is reciprocity, and when there is antireciprocity, which means signals of equal amplitudes but with the phase shifts differing by 180° for transmission in the two directions.A known reciprocity theorem for stations in the magnetic meridian plane is extended and shown to apply in a modified form for any azimuth of propagation, but the extension is valid only under the approximations of ray theory.The results are applied to the theory of polarization fading and it is shown that there can be a time displacement of the fading cycles at the two ends of the ray path.

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