For this tilt dependent model, four sets of model coefficients are available for four levels of magnetic activity as parameterized by Kp. It is valid out to 17 Earth radii. The model is expressed as second order power series expansions in solar magnetic coordinates, quadratic in position and linear in tilt. Model coefficients (17) were obtained by a least-square-fit to 12,616 vector field measurements from 451 orbits of four IMP satellites between 1966 and 1972. The effect of localized current systems like the ring current and sheet currents in the tail are not particularly well modeled by these quadratic expansions. The program includes the GSFC(12/66) main field model for the representation of the internal (core) part of Earth's total magnetic field. A simple offset dipole field can be chosen instead of the spherical harmonics GSFC model, to reduce the computation time.
D. H. Fairfield and G. D. Mead, Magnetospheric Mapping with a Quantitative Geomagnetic Field Model, J. Geophys. Res. 80, 535, 1975.