The self-consistent geomagnetic tail under static conditions

A self-consistent calculation of the magnetic field and plasma distribution in the magnetotail has been undertaken for static conditions. We find the best agreement with experimental observations by satellite in the tail for an isotropic particle pitch angle distribution, a slow decrease of magnetic field intensity as a function of distance from the Earth | x| ^-0.3, and a northward field in the equatorial plane of about 1 gamma at the position of the lunar orbit. Knowing the field and plasma distribution we calculate the sources of the electrical current and find that the magnetic field in the tail can be supported entirely by solar wind drifting into the curved and diminishing magnetic field of the magnetotail. Furthermore the plasma present in the tail at any one instant is swept out in a very short time due to its large curvature drift velocity; the constant plasma sheet is maintained by constant renewal of entering solar wind plasma.