三维MHD背景场下太阳高能粒子平均自由程模拟

太阳高能粒子（SEP）的平均自由程是研究SEP传播的重要参数，由SEP的物理性质和太阳风物理性质决定.使用MHD-SEP模型对三维MHD背景场下的平均自由程进行了探讨，利用该模型具有可提供接近物理真实的太阳风背景场的优势，对SEP的平均自由程进行了定性分析.分别对太阳活动高年和低年选取2个卡林顿周进行模拟，定性分析其空间变化，并研究平均自由程与径向太阳风速度的相关性.结果表明:该方法得到的平均自由程空间分布与以往研究得到的关于平均自由程的结论相吻合，可以用来定性确立平行平均自由程；该模型可以反映不同事件中平行平均自由程分布的不同特征；表现了平均自由程与径向太阳风速度有很好的负相关关系.结果可为未来缓变SEP平均自由程研究作参考. 

Simulation of Mean Free Path of Solar Energetic Particles in Three-dimensional MHD Background

The mean free path of SEP is an important parameter in the study of SEP propagation in space physics, which is determined by the physical properties of SEP and solar wind. In this paper, the MHD-SEP model is used to discuss the mean free path under the three-dimensional MHD background field. The advantage of this model is that it has the solar wind background field tending to the real physical model. Two CRs were selected to simulate the high and low years of solar activity, and the spatial changes were qualitatively analyzed, and the correlation between mean free path and radial solar wind speed was studied. The conclusion of the spatial distribution of the mean free equation obtained by this method can be consistent with that obtained by previous scholars, and can be used to qualitatively establish the parallel mean free equation. The model can reflect the different characteristics of the distribution and value of the parallel mean free path in different events. It shows that the average free path depends on the radial direction and has a good negative correlation with the radial solar wind velocity. This work can be used as a reference for future research on the mean free path of SEP.