R. Michael Jones; Judith J. Stephenson


This report describes an accurate, versatile FORTRAN computer program for tracing rays through an anisotropic medium whose index of refraction varies continuously in three dimensions. Although developed to calculate the propagation of radio waves in the ionosphere, the program can be easily modified to do other types of ray tracing because of its organization into subroutines.

The program can represent the refractive index by either the Appleton-Hartree or the Sen-Wyller formula, and has several ionospheric models for electron density, perturbations to the electron density (irregularities), the earth's magnetic field, and electron collision frequency.

For each path, the program can calculate group path length, phase path length, absorption, Doppler shift due to a time-varying ionosphere, and geometrical path length. In addition to printing these parameters and the direction of the wave normal at various points along the ray path, the program can plot the projection of the ray path on any vertical plane or on the ground and punch the main characteristics of each ray path on cards.

The documentation includes equations, flow charts, program listings with comments, definitions of program variables, deck set-ups, description of input and output, and a sample case.

See errata sheet for corrections.

Keywords: ionosphere; computer program; Appleton-Hartree formula; radio waves; ray tracing; Sen-Wyller formula; three-dimensional

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