The magnetic field of a model radiation belt, numerically computed

The magnetic field of a model ring-current belt encircling the earth symmetrically is numerically calculated, to a first approximation, for a particular model belt already discussed by Akasofu and Chapman [1961a]. They calculated the first approximation to the field only for points in the equatorial plane. The whole distribution of the field is here discussed, and for a particular intensity of the belt the calculation is carried to a second approximation. It is shown that over the earth's surface the field of the ring current is nearly uniform, though in auroral latitudes the diamagnetism of the belt produces an insignificant irregularity in the field disturbance. The model belt considered here is one whose center line is connected with the auroral zone by the dipole field lines of force; its particles have not yet been observed directly. Its existence is suggested by the quiet-day anomaly of the satellite-observed magnetic field at that distance. The known Van Allen radiation belts seem likely to contribute little to the ring current field, but during magnetic storms the radius of the belt mainly responsible for this field is probably less than 6 earth radii.