The geometry of the Earth's magnetic field at ionospheric heights

This paper is mainly concerned with the geometry of radio-wave propagation associated with the earth's magnetic field. A theoretical method is presented which can be used to determine the angle that the earth's magnetic field makes with the direction of propagation, irrespective of geographic location and for transmissions directed at any azimuth and elevation orientation. The techniques of matrix-coordinate transformations are utilized in this analysis by assuming that the earth's magnetic field can be approximated by a centered magnetic dipole. Computations are given for one location in the Northern Hemisphere. The resultant data are compared with those obtained by the well-known graphical method in which ground-observed magnetic data are scaled from isomagnetic maps.