MHD Simulations Of The Magnetopause Structure

Because of the lack of sufficient satellite data, there are few high-latitude magnetopause shape models. With the development of computer technology and numerical simulation methods, the simulation data based on physical theory of magnetopause is becoming effective substitutes. In this paper, the global magnetohydrodynamics (MHD) numerical simulation data of the coupled model of solar wind-magnetosphere-ionosphere system are used to study the three-dimensional structure of the magnetopause and its shape at distinct conditions. We study the position and shape of the magnetopause under several solar wind dynamic pressure (D) and interplanetary magnetic field (IMF) conditions.The simulation results of equatorial plane show that the subsolar position (r0) of the magnetopause is mainly controlled by Dp with significant decreasing ofr0as Dp increases. At certain Dp, when southern IMF Bz(Bz<0) decreases to zero, then shifts to northward (Bz>0) and increases, the subsolar position r0keeps gradually increasing. For all cases studied here, the flare angle (φ) of the magnetopause experiences very small change. This provides an eviden-ce for the structural self-similarity of the magnetopause in equatorial plane. C-ompared with the empirical low-latitude magnetopause model of Shue98, MHD simulation can reproduce the dependence of the subsolar point r0on Dp an-d Bz. As to the flare angle φ, although the difference between our MHD si-mulation and empirical model for each case is very small, the variation of φ with IMF Bz in MHD results is not the linear relationship as shown in em-pirical model.It is found that in the noon-midnight meridian plane, the magnetopause shape has evident concave features, which is consistent with the experience model of Boardsen et al.[2000]. The cusp structure of the meridional plane does not follow the model of Shue et al.[1997] for low-latitude magnetopause. By analyzing the change of the magnetopause shape parameters on the noon-midnight meridian plane, we obtain the same results with that of empirical model. The simulation results show that in the noon midnight meridian plane magnetopause shape has a concave structure. And at certain Dp, when southern IMF Bz(Bz<0) increases the subsolar position (r0) of the magnetopause decreases, when northward (Bz>0) increases, the subsolar position r0keeps gradually increasing, with significant decreasing of r0as Dp increases. For all cases studied here, the flare angle of the magnetopause increases when (Bz<0) increases.The simulation results are compared with the empirical model of Shue97and BOO. It is clear that the noon-midnight meridian plane has concave structure. In addition the variations of the magnetopause shape with interstellar conditions are also presented in this paper. These results provide some basis for further study of three-dimensional magnetopause structure and the forecasting of magnetopause shape for space weather.