The electric field model of the earth's magnetotail

The electric field in the Earth's magnetosphere is the main driving force of plasma motion there. The magnetospheric electric field is now generally taken to be a uniform dawn-dusk field or a projected field. In this work it is assumed that magnetic field lines are the equipotential lines of electric field, and that the electric field of the terrestrial ionosphere is taken to be the magnetospheric electric field projected along magnetic field lines. By using Tsyganenko's magnetic field model (T89), the ionospheric electric field is projected to the magnetotail, so obtaining a new model of magnetospheric electric field. In this paper a comparison between the bipolar magnetic field and the projection of the T89 model is made. A break of the restriction to bipolar magnetic fields has been achieved, which has a large range of application for the magnetosphere.