Approximate solutions are given for the shape of the boundary separating a steady neutral stream of ionized solar corpuscles from the combined magnetic fields of a three-dimensional dipole and an equatorial ring current. Results are presented for the traces of the boundary in the geomagnetic meridian plane containing the sun-earth line for several orientations of the latter relative to the dipole axis, and for the trace of the boundary in the geomagnetic equatorial plane for the case in which the dipole axis is normal to the sun-earth line. It is found that the presence of a ring current having values for the diameter and strength of the order proposed to explain in the magnetometer data from Pioneer I and Pioneer V has the effect of greatly increasing the size, as well as altering the form, of the region within which the geomagnetic field is confined.