On the Calculation of Mode Conversion at a Graded Height Change in the Earth‐Ionosphere Waveguide at VLF

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Abstract
A multistep model is used to simulate the transition between the day and night portions of the earth‐ionosphere waveguide. A convenient simplification is the justified neglect of all reflected modes. On the other hand, forward mode conversion (and reconversion) is accounted for. The analytical method involves the multiplication of square matrices which correspond individually to the conversion at the various steps. The calculations are carried through for a sharply bounded ionosphere and a perfectly conducting ground. Earth curvature is allowed for but the influence of the earth's magnetic field is neglected. A calculated example for 20 kHz indicates that the transition length Δd between day and night influences the amount of mode conversion.