Graphic data on the Earth's main magnetic field in space

The applicability of a dipole representation of the earth's main magnetic field at high altitudes is discussed. Useful characteristics of the centered dipole approximation are presented in simple graphical form. Data that can be obtained from the charts include location of field lines, arc length along a field line, electron gyrofrequency, inclination (or dip), magnetic-field intensity, magnitude and direction of the gradient of the earth's field, and radius of curvature of the lines of force. The resulting accuracy is believed sufficient for many purposes.