日冕极紫外波的数值研究

The most intense energetic activity in the solar system is the solar eruption that produces solar flare, eruptive prominence, and coronal mass ejection (CME). During the process, a large number of magnetized energetic plasmas are ejected into the interplanetary space within a short timescale, and hence disturb spatial and planetary magnetic field and significantly affect satellite operation, aviation power, human space exploration, communication and so on. One interesting and important phenomenon closely associated with CMEs is the globally propagating wave-like disturbance in the corona, i.e. the extreme ultraviolet (EUV) waves. It can help us to study the properties of the solar eruption. Up to the present, many basic questions about the EUV waves still remain unclear. Therefore, a further investigation on the EUV waves is essential. The main aim of this project is to 1) numerically study the detailed evolutionary features of the EUV waves and their propagation in the process of eruption，2) uncover processes not commonly discussed but potentially crucial to understand the physical nature of the EUV waves. This project will conduct a relatively comprehensive study on the EUV waves based upon the observations and numerical simulations. We expect to obtain an overall understanding about the EUV waves, the trigger mechanisms, application on the coronal seismology, and establish a solid foundation for our future studies.

剧烈太阳爆发现象,如日冕物质抛射(Coronal Mass Ejection；CME)、太阳耀斑等发生时,会在较短时间内抛射出大量高能带电粒子流，这些高能物质会对空间天气造成强烈扰动，而发生在日冕层的大尺度日冕极紫外波（Extreme Ultraviolet; EUV）与太阳爆发现象密不可分。EUV波携带了丰富的物理信息，这些信息为正确理解日冕大气中各种复杂爆发现象提供了可靠的物理依据。目前对EUV波的研究得到广泛关注，但一些基本物理问题仍无定论，有待进一步深入研究。本项目拟采用数值模拟方法，数值研究EUV波细节演化特征及传播过程，结合观测事例揭示其物理本质、探讨其产生机制，并提出合理的解释模型。另外，拟数值研究EUV波传播过程中，相关日冕物理参量的变化，为探讨EUV波在冕震学上的应用奠定基础。本项目拟对EUV波做较为全面的数值研究，期望对其有一个较为完整的掌握，为今后进一步研究奠定基础。

与太阳高能事件密切相关的日冕极紫外（extreme ultraviolet,缩写为EUV）波是发生在太阳日冕层的很壮观的扰动，这一扰动现象为我们深入研究大尺度太阳爆发现象提供了很多线索。但是目前人们对其物理本质、产生机制及与之相关的等离子体特征等都还存在很大争议。我们采用数值模拟的方法，对EUV波的细节演化特征进行了研究。我们使用预处理技术对数值算法进行了优化，理论和实验结果表明，对算法预处理后，收敛速度加快，计算精度也得到了提高，同时还保证了计算的稳定性。我们使用优化后的算法，对EUV波演化所需要的光球磁场位形做了数值研究，结果显示磁绳的平衡高度与背景磁场的相对强度呈近似幂函数分布，并且磁绳初始半径越大，磁绳越容易逃逸出去。这表明暗条半径的大小对空间天气的预报工作，尤其是太阳爆发的预报有一定的参考价值。在优化算法的基础上，我们延展了演化的空间尺度和时间尺度，数值研究了EUV波动传播过程中的细节演化特征，尤其是后期演化，并对其物理本质进行了深入探讨。