The investigators will develop a new generation magnetosheath model for a wide range of solar wind parameters and realistic magnetopause shapes. Many studies of the solar wind-magnetosphere interaction require quantitative models for magnetosheath parameters. Such models are needed to time the arrival of solar wind features, determine whether conditions at the magnetopause are favorable for reconnection, and to describe the magnetosheath plasma parameter input into the cusp and mantle. The only existing models are gas dynamic models which neglect the magnetic field. The investigators will develop a new model based on magnetohydrodynamics (MHD). The results of this model will be compared to existing gas dynamic models and to empirical models developed from in situ satellite data. The results will also be used to discriminate between various proposed modes of magnetic merging on the dayside magnetopause. The MHD magnetosheath model will help improve the understanding of the plasma processes and energy transfer in the solar wind-magnetosphere-ionosphere system and help assess the terrestrial environmental variations due to changes in the solar wind and interplanetary magnetic field.