Magnetosphere-ionosphere coupling by Alfvén waves at midlatitudes

Many numerical models of magnetospheric dynamics treat the ionosphere as an inner boundary condition. These models have traditionally used the current continuity condition, treating the ionosphere as a sheet current in which the electric field is electrostatic. A more general boundary condition is suggested that not only is more complete, but also straightforward to implement. Results from a model using this boundary condition applied to the excitation of field line resonances in the magnetosphere are presented. 1