On the effect of a ring current on the terminal shape of the geomagnetic field

The interaction between a neutral stream of ionized solar corpuscles and the combined magnetic fields of a three-dimensional dipole and an equatorial ring current is investigated. It is assumed that the stream is confined to the exterior and the magnetic field to the interior of a hollow, the boundary of which is defined by a thin current sheath. The shape of the hollow is sought by application of an approximate method of solution. Results are presented for the traces of the boundary in the equatorial plane and the meridian plane containing the dipole axis and the sun-earth line for the case in which the dipole axis is normal to the sunearth line. It is found that the presence of the ring current has the effect of greatly increasing the size, as well as altering the form, of the region bounded by the current sheath. The calculated results are, moreover, in essential agreement with the observations when representative values are inserted for the properties of the ring current and the solar corpuscular stream.