A physics based nonlinear dynamical model for the solar wind driven magnetosphere-ionosphere system

The predictive performance of a six-dimensional nonlinear dynamical model o f the coupled magnetosphere-ionosphere system is compared to magnetospheric activity data. The model couples the basic energy components of the night- side magnetotail to the ionosphere by the region 1 currents. It predicts bo th the state of the geotail and the ionospheric westward electrojet index f rom the value of the solar wind speed. Except for the ionospheric dissipati on, the system is both Kirchhoffian and Hamiltonian. This ensures that the solar wind input power is divided into physically realizable sub power comp onents, a property not shared by signal processing filters. All the model p arameters can be calculated analytically for different substorm scenarios. Agreement between the predicted and observed magnetospheric indices improve s significantly when the system is coupled to particle simulations to produ ce realistic parameters for the model. Including the nonlinear increase of the ionospheric conductance with power deposited in the ionosphere is also essential. (C) 1998 Elsevier Science Ltd. All rights reserved.