中文摘要：

利用全球磁流体力学（MHD）的模拟结果，研究了太阳风压力系数与上游太阳风参数和日下点磁层顶张角的相关性．在识别出日下点附近磁层顶位置后，通过拟合得到日下点附近的磁层顶张角．在考虑上游太阳风中的磁压和热压以及磁层顶外侧的太阳风动压的情况下，计算了太阳风压力系数．通过分析行星际磁场不同方向时太阳风动压在日地连线上与磁压和热压的转化关系，详细研究了太阳风参数和日下点磁层顶张角对太阳风压力系数的影响，得到以下相关结论：（1）在北向行星际磁场较大（B：≥5nT）时，磁层顶外侧磁压占主导，南向行星际磁场时磁层顶外侧热压占主导；（2）太阳风压力系数随着行星际磁场的增大而增大，随着行星际磁场时钟角的增大而减小；并且在行星际磁场大小和其他太阳风条件相同时，北向行星际磁场时的太阳风压力系数要大于南向行星际磁场时的；北向行星际磁场时，太阳风压力系数随着太阳风动压的增大而减小，南向行星际磁场时，太阳风压力系数随着太阳风动压的增大而增大；以上结论是对观测结果的扩展；（3）最后，我们还发现太阳风压力系数随着日下点磁层顶张角的增大而增大．

英文摘要：

A three-dimensional adaptive magnetohydrodynamic （MHD） model is used to study the dependences of the solar wind pressure coefficient on the upstream solar wind parameters and the subsolar magnetopause flaring angle. The subsolar magnetopauses are determined under the different solar wind conditions, so that we can fit the flaring angles of the subsolar magnetopause. We calculate the solar wind pressure coefficient by considering the thermal pressure and the magnetic pressure upstream the solar wind, as well as the dynamic pressure outside the magnetopause. By investigating the pressure conversion among the dynamic, thermal and magnetic pressure on the Sun-Earth line for the different orientations of the interplanetary magnetic field （IMF）, we study the influence of the upstream solar wind parameters and the subsolar magnetopause flaring angle on the solar wind pressure coefficient, and the conclusions are as follows. （1） For the larger northward IMF （B≥5 nT）, outside the magnetopause the magnetic pressure is dominant, while the thermal pressure is dominant for the southward IMF;（2） The solar wind pressure coefficient is increased with the increasing IMF, and decreased with the IMF clock angle. Under the same other solar wind conditions, the solar wind pressure coefficient for the northward IMF is larger than that for the southward IMF. For the northward IMF the solar wind pressure coefficient decreases with the increasing solar wind dynamic pressure, while the solar wind pressure coefficient increases with the increasing dynamic pressure for southward IMF; the above results are the extensions of the observations; （3） Moreover, for the first time, we find that the solar wind pressure coefficient is increased with the increasing subsolar magnetopause flaring angle.