磁鞘等离子体密度统计建模

Statistical Modeling Research on the Magnetosheath Plasma Density

利用理想磁流体LFM模型的模拟数据,基于非参数统计方法对2004年11月14日03:00 UT-07:00 UT磁暴恢复相期间磁鞘等离子体平均密度进行建模.分析磁鞘等离子体平均密度与上游太阳风参数、行星际磁场参数及地磁扰动参数的统计关系,建立基于数据降维的经验模型.结果表明,电离层扰动强度因子、太阳风-磁层耦合强度因子和日地空间因果链耦合强度因子是影响磁鞘等离子体平均密度的三个主要方面.磁暴恢复相期间电离层上行离子是磁层环电流和磁尾等离子体的重要离子来源.建模分析过程表明,利用经验模型对空间物理过程开展建模,数据的严重多重共线性通常会导致模型的精度较差.而利用SIR和LPR建立的磁鞘等离子体平均密度随相关参数变化的经验模型可以有效解决该问题,具有较好的预测精度,统计特征显著.

By using the simulation data of the ideal MHD LFM model, the model of the mean plas- ma density of the magnetosheath from 03：00 UT to 07：00 UT on November 14, 2004 is established based on the Sliced Inverse Regression （SIR） and Local Polynomial Regression （LPR） method. The statistical relationship between the mean plasma density and the upstream solar wind parameters, the interplanetary magnetic field, and the geomagnetic disturbance indices are analyzed. The results show that the ionospheric disturbance intensity factor, the solar wind-magnetosphere coupling inten- sity factor, and the Sun-Earth coupling intensity factor are the three main factors which influence the plasma density of the magnetosheath. The up-flowing ions are the important source for magneto- sphere circular current and magnetotail plasma during the recovery phase. The analyses show that,as modeling the process of space physics by the empirical regression method, the multi-collinearity problem usually leads to the poor accuracy of the model. However, the statistical models built by the non-parametric statistical method of SIP and LPR can efficiently solve the problems above.