The Equilibrium Magnetosphere.

We present a method of computing the day-side global earth magnetic field which is in equilibrium with the plasma pressure based on satellite observations at a local region of the magnetosphere. The method, which utilizes a Perturbation around a dipole magnetic field, involves computation of the global plasma pressure profile, P ppd (r,theta) and P sub || (r,theta) based on the equatorial (anisotropic) pressure data P ppd (r,pi/2) and P sub ||(r,pi/2), derivation of the current profile which satisfies the equilibrium condition, JXB-DELTA.-> over P=O, and computation of the magnetic field using the current profile and the boundary current produced by the solar wind. The method is applied for the AMPTE data and the result of computation is found to compare reasonably well with the observed magnetic field profile near the geomagnetic equator.