New Version of MODESRCH using Interpolated Values of the Magnetoionic Reflection Coefficients

摘要

For low frequency cases of nighttime propagation, an elevated antenna, or distances close to the transmitter, the propagation constants for a large number of modes must be found to adequately represent the fields in the earth-ionosphere waveguide. Most of the cost in using MODESRCH to obtain these mode constants has been in performing full wave integrations to obtain the reflection matrix, R. Until recently it had been necessary to carry out several fullwave integration each for R and its derivative with respect to the angle of incidence, theta, for each waveguide mode. As a result of this present effort it has become possible to obtain interpolated values of R which are more than adequate to describe the earth-ionosphere mode constants. The approach used is to transform the reflection matrix, R, obtained from a fullwave integration, into magnetoionic reflection coefficients, subscript oe. Each coefficient represents the complex amplitude of the ordinary or extraordinary. The equations defining the magnetoionic eigenvectors, which are required for this transformation, have been derived for the free space limit, so that they are applicable to a height that is below most of the ionization. Experience in use of the algorithm has shown that for eigenangles not too near branch points, the complex logs of the elements of superscript oe vary so nearly linearly that values of R derived from interpolated values of ln(superscript oe) are more than adequate for use in determining mode constants. It is believed that the reason for the nearly linear variation is that each represents reflection from only one discrete complex height.