时变行星际太阳风模拟及其结果评估

Time-dependent simulation and result validation of interplanetary solar wind

背景太阳风对于地球附近的空间环境有着重要的影响,三维磁流体力学太阳风模型是背景太阳风研究和预报的重要工具.通过太阳光球磁场数据驱动的边界条件,我们发展了一个时变的行星际三维磁流体力学太阳风模型.使用这个模型,我们模拟了2008年全年的行星际背景太阳风,分析了该年太阳风结构全球特征的演化和行星际局地观测与日冕结构间的联系.实现了一套太阳风连续参数和特征结构模拟质量的定量评估方法.对2008年模拟结果的评估表明,模型较好地重现了背景太阳风的大尺度特征.模拟与观测速度间的相关性系数达到了0.6以上,行星际磁场强度与观测吻合得较好,捕获了全部的行星际磁场极性反转和82.76%的流相互作用区,行星际磁场极性反转的误报率仅为6.67%,流相互作用区的误报率仅为11.11%,两种结构的到达时间误差在1天左右.同时,通过综合分析评估结果,我们明确了高速流结构、内边界磁场分布等模型在进一步改进中需要重点注意的问题.

The ambient solar wind has critical influence on the space environment near the Earth.Three dimensional magnetohydrodynamics solar wind model is an important tool for research and forecast of ambient solar wind.Employing boundary condition driven by solar photospheric magnetic field observation,we develop a time-dependent three dimensional magnetohydrodynamics interplanetary solar wind model.Using this model,we simulate the ambient solar wind of Year2008,and analyze the evolution of global solar wind structures and the connection between interplanetary in-situ measurements and corona structures during that year.We realize a set of procedures,which evaluate the quality of predictions for both continuous solar wind parameters and characteristic structures of the solar wind.The evaluation results indicate that our model satisfactorily reproduces the large scale structure of the ambient solar wind during Year2008.The correlation coefficient between observed and simulated speed is higher than0.6.The strength of simulated interplanetary magnetic field matches observation well.All interplanetary magnetic field reverses and82.76%of the stream interaction regions are captured by our model.The false alarm rate of the interplanetary magnetic field reverse prediction is only6.67%while that of the stream interaction region is only11.11%.The errors in predicting the arrival time of these two structures are about1day.Through comprehensive analysis of the evaluation result,we also gain understanding of the major issue of model improvement,including the structure of the high speed flow and the distribution of magnetic field at the inner boundary.