【作者】 王磊；

【导师】 冯学尚；

【作者基本信息】 哈尔滨工业大学 ， 航空宇航科学与技术， 2024， 硕士

【摘要】 在最近几年中,基于强大计算能力的三维日冕行星际过程数值模型已成为灾害性空间天气预测建模的核心工具。日冕磁场对于行星际磁场、背景太阳风的形成和耀斑、日冕物质抛射的产生有重要影响,研究和分析日冕磁场具有重要的科学意义和应用价值。势场源表面模型是研究日冕磁场的一种常用数值模型。利用解析和观测输入,对基于伽辽金方法的势场源表面(Direct Discontinuous Galerkin For Potential Field Source Surface,DDG-PFSS)模型进行了模拟验证。利用解析输入,发现DDG-PFSS求解器的数值解与解析解的误差有限。通过解析算例,证明了求解器的程序收敛,数值算法具有三阶精度;绘制的解析解与数值解的磁拓扑结构基本一致,DDG-PFSS数值求解器与解析解的误差较小;提高网格分辨率可以使数值外推场向量与解析磁场向量之间的矢量误差降低;比较数值解与解析解的相对误差随径向距离的变化,发现模拟区域内部的相对误差小于外边界附近的相对误差。利用观测输入,对比发现DDG-PFSS求解器与球谐展开法求解器的模拟结果基本一致,DDG-PFSS求解器能够重现观测到的日冕磁场大尺度结构。将求解器捕获的冕洞分布与观测数据进行对比,发现除了少许低纬小冕洞外,求解器能够成功地捕获观测到的冕洞分布区域;将求解器导出的磁场配置Wang-Sheeley-Arge模型和Arge-Pizzo运动学演化模型得到1 AU处的太阳风速度,与OMNI观测数据进行对比,结果显示基本上捕获了观测数据中的高速流和低速流结构出现的范围。模型验证实验结果表明DDG-PFSS数值算法具有三阶精度,与解析解的误差有限,能够重现观测到的日冕磁场大尺度结构,证明了求解器的有效性。更多还原

【Abstract】 In recent years,three-dimensional numerical models of coronal interplanetary processes based on powerful computational capabilities have become a central tool for predictive modeling of catastrophic space weather.The coronal magnetic field has an important influence on the interplanetary magnetic field,the formation of the background solar wind and the generation of flares and coronal mass ejections,and the study and analysis of the coronal magnetic field is of great scientific significance and application value.The potential field source surface model is a commonly used numerical model to study the coronal magnetic field.The direct discontinuous Galerkin for potential field source surface(DDG-PFSS)model based on the Galerkin method is simulated and validated using analytical and observational inputs.Using the analytic input,it is found that the error between the numerical and analytic solutions of the DDG-PFSS solver is limited.By analyzing the examples,it is demonstrated that the program of the solver converges and the numerical algorithm has third-order accuracy;the magnetic topologies of the plotted analytical and numerical solutions are basically the same,and the error between the DDG-PFSS numerical solver and the analytical solution is small;increasing the mesh resolution reduces the vectorial error between the numerical extrapolated field vectors and the analytical magnetic field vectors;and comparing the change of the relative errors between the numerical and analytical solutions with the radial distance,it is found that the relative error inside the simulation region is smaller than that near the outer boundary.Using the observational input,the comparison shows that the simulation results of the DDG-PFSS solver and the spherical harmonic expansion method solver are basically consistent,and the DDG-PFSS solver is able to reproduce the observed large-scale structure of the coronal magnetic field.Comparing the coronal hole distribution captured by the solver with the observed data,it is found that the solver is able to successfully capture the observed coronal hole distribution region except for a few small low-latitude coronal holes;the solar wind velocity at 1 AU is obtained from the magnetic field configurations of the Wang-Sheeley-Arge model and ArgePizzo kinematical evolution model derived from the solver,and the results show that the solar wind velocity at 1 AU is basically captured by the DDG-PFSS solver and the spherical harmonic expansion method solver,and the results are in general consistent with those of the OMNI observed data.The results are shown to essentially capture the range of occurrences of high-and low-speed flow structures in the observations.The results of the model validation experiments show that the DDG-PFSS numerical algorithm has a third-order accuracy with a finite error from the analytical solution,and is able to reproduce the observed large-scale structure of the coronal magnetic field,proving the effectiveness of the solver.更多还原