THE FIELD OF A SCREENED MAGNETIC DIPOLE

The purpose of this note is to quantitatively study the asymptotic beh avior of the dipole magnetic field in the tail region of a paraboloida l or cylindrical model of the magnetosphere, assuming the complete scr eening of the internal field by magnetopause currents. This screening assumption is equivalent to imposing the boundary condition that the n ormal component of the magnetic field is zero at the magnetopause. Wit h this boundary condition, the screened dipole field falls off exponen tially with distance down the tail, in sharp contrast to the bare dipo le field. Analytic expressions for a cylindrical and paraboloidal magn etopause are given.