Model study of plasmapause motion

The ambient plasma in the equatorial plane is predominantly subject to the E×B drift. By approximating the earth's magnetic field by a dipole, characteristic steady state streamlines in the equatorial plane are determined, assuming the interaction between the solar wind and the magnetosphere is characterized by a constant electric field directed from dawn to dusk in the equatorial plane. The steady state plasmapause corresponds to the stagnation streamline in this flow. If the magnitude of the dawn-dusk field is suddenly increased, the plasmasphere bulge moves toward the sun. By suddenly decreasing the magnitude of this field, the bulge can be made to corotate with the earth. The model computations indicate that the spatial configuration of the plasmapause can be very complex, especially near the bulge, because its position depends upon the past history of the magnetosphere.