空间科学部知识库

近地空间的太阳风参数预报具有重要的科学研究意义和实际应用价值，三维磁流体力学（MHD）数值模拟是太阳风参数预报的重要手段.本文建立了一套基于经验模型的三维MHD数值模型.模型的内边界设置在0.1天文单位（AU）处，在六片网格系统下利用TVD Lax-Friedrich格式求解理想MHD方程组，采用扩散法消除磁场的散度.模型以GONG的观测磁图作为输入数据，利用经验模型并结合卫星观测特征确定内边界条件.边界条件中保留了6个可调参数，以便适当调整参数使其方便适合模拟不同太阳活动期的太阳风.利用该模型分别模拟了2007年和2016年的背景太阳风，得到了太阳风速度、密度、温度和磁场强度，这些参数与ACE/WIND卫星观测符合较好.

The prediction of solar wind parameters near the Earth has important scientific research significance and practical application value. Three-dimensional magnetohydrodynamics (MHD) numerical simulation is a primary tool in the prediction of solar wind parameters. This paper presents a three-dimensional MHD numerical model which can be used to simulate the background solar wind in the interplanetary space. The inner boundary of the model is set at 0.1 astronomical unit (AU) and a six-component grid system is employed in the computation domain. The ideal MHD equations are solved by using the total variation diminution (TVD) Lax-Friedrich scheme, and the divergence of the magnetic field is eliminated by a diffusion method. This model uses magnetogram synoptic map images from the Global Oscillation Network Group (GONG) observation as input data. The empirical Wang-Sheeley-Arge (WSA) relation is used to assign solar wind speed at the inner boundary, while density and temperature are specified according to the characteristics of satellite observations. There are six free parameters in the boundary conditions, which can be tuned to simulate the solar wind for different phases of the solar cycle. This model is used to simulate the background solar wind in 2007 and 2016, respectively, and the simulated solar wind parameters (including speed, density, temperature, and the magnetic field strength) are in good agreement with the ACE/WIND satellite observations.