Characteristic waves

The familiar quasi-homogeneous (ray) treatment of the ionosphere shows that in a slowly varying ionosphere there are two and only two possible types of independent propagating waves called the magneto-ionic components. In the case of normal incidence, these components have the well-recognized property that the polarization of a reflected wave of one type is identical to that of an incident wave of the same type. However, it does not seem to have been appreciated that, in general, for linear anisotropic reflecting media of any degree of inhomogeneity, there exist two and only two characteristic polarizations having the latter property. It is shown that the characteristic polarizations can be determined from three experiments in which three different known polarizations are transmitted and the resulting reflected polarizations are measured. The information thus obtained is also sufficient to determine the ratio Of the reflection coefficients of the two characteristic waves. In the special case of the homogeneous ionosphere it is shown that the number of experiments of the above type can be reduced to two.