Solar wind flow around the earth's magnetosphere

Stationary isotropic, quasistationary isotropic, and anisotropic two-dimensional MHD models of plasma flow between a bow shock and the magnetopause near the Earth-Sun line are considered. A comparison of the model calculations with experimental data indicates that the modeled magnetic barrier and the layer with decreased plasma density are most clearly defined and less pronounced when IMF is southward and northward, respectively. The plasma flow topology in the magnetosheath has been studied using one magnetosheath crossing on November 5, 1977, as an example, and a rather good agreement has been obtained between theoretical and experimental data. The empirical relationship between the magnetopause location, solar wind dynamic pressure ahead of a bow shock, and the magnetic field strength and orientation before the magnetopause has been obtained. It has been indicated that the magnetopause location can be predicted based on the solar wind parameters using the relationships between the magnetic field in the magnetosheath and in the solar wind obtained within the scope of the proposed model. It has been demonstrated that the Birkeland-loop current responsible for a decreased magnetic field strength in the dayside magnetosphere cannot be caused by a breaking of magnetopause currents and can be generated by certain magnetosheath currents. The proton temperature anisotropy in the magnetosheath has been studied. It has been indicated that the temperature isotropization timescale (tau) varies from several seconds immediately behind a bow shock tor 50 s in the central part of the magnetosheath and to 20 s near the magnetopause.