EUV波与冕洞相互作用的观测研究

EUV waves,also known as EUV Imaging Telescope (EIT) waves,are large-scale transient coronal disturbance observed in EUV wavelengthes. The physical nature of EUV waves is still an active research topict since 1998 when the first coronal wave was observed. Some researchers believe EUV waves are fast mode MHD waves, while other researchers insist that coronal waves are non-wave propagating disturbances. Coronal holes refer to the dark coronal areas where the density is very low. Whether EUV waves will reflect at the borders of coronal holes is an evidence of true waves or not. Few work have been done on this topic because of previous low resolutional observation and the deem of coronal hole boundaries. We plan to study the reaction between EUV waves and coronal holes based on latest observational data. First of all, by looking through the movies made from the data of the Solar Dynamics Observatory (SDO) in multi-wavelengthes with best temporal and spacial resolution, we will choose the typical EUV waves which have a close relationship with their surrounding coronal holes. We will analyze the propagational dynamics of the EUV waves and the change of magnetic structure and physical parameters in the coronal holes. Then we will provide a statistical result of whether and how many EUV waves will be reflected at the boundaries of coronal holes and whether and how many of them could pass through coronal holes.We will also show the values of the physical parameters in coronal holes before and after EUV waves arrive. At last, we will conclude whether EUV waves are true waves or not and develop a simple model on the reaction between EUV waves and cororal holes.

EUV波，也称为EIT波，是指在远紫外波段观测到的太阳日冕中大尺度的扰动。自1998首次被发现至今，EUV波的本质一直是太阳物理领域非常有争议且十分热门的课题。一些学者认为它是真正快磁声波，而另外一些学者则认为不是波。冕洞是日冕中的低密度区域，对EUV波的传播有重要影响。EUV波在冕洞边界的反射与否是验证EUV波是否为真正波的有力证据。目前这个领域还没有系统的研究。本项目拟从观测方面着手对EUV波和冕洞的相互作用进行研究。首先借助于最近升空的SDO卫星提供的多波段的、高时空分辨率的资料，筛选出与冕洞有明显相互作用的EUV波；然后对EUV波的动力学特征以及冕洞的结构变化进行研究。对EUV波在冕洞边界附近是否发生反射以及能否绕过冕洞继续传播给出统计的结果；对冕洞与EUV波相互作用前后的结构和物理参数变化给出准确的描述。最后得到EUV波是否为真正波的结论，并建立EUV波和冕洞相互作用的简单模型。

本项目主要以EUV波、冕洞以及它们之间的相互作用作为主要研究对象。EUV波是指在远紫外波段观测到的太阳日冕中大尺度的扰动，其本质（波或非波）是太阳物理领域非常有争议且十分热门的课题。冕洞是日冕中的低密度、单极磁场区域。项目初衷是通过EUV波在冕洞边界的反射与否是验证EUV波是否为真正波。但在研究过程中，我们发现一些的新的现象，也将其加入到了研究内容。因此，我们的研究不局限于EUV波和和冕洞。借助与SDO卫星提供的多波段、高时空分辨率的远紫外波段的图像资料，我们对几个典型的太阳爆发事件进行了研究。主要结果如下：a) EUV波在冕洞边界存在明显的反射，支持EUV波含真正波的成分; b) 强烈的EUV波可以导致冕洞的形成；c）同一活动区连续爆发的EUV波可以导致暗条内等离子的强烈震荡，甚至导致太阳龙卷风出现；d）失败的暗条爆发伴随强的耀斑，但没有产生EUV波和日冕物质抛射，支持EUV波由CME而非耀斑触发；e）发现“拴绳切断”的直接观测证据。这些结果对理解太阳上大尺度的爆发活动机制以及日冕中大尺度扰动的本质等有重要作用，同时对空间天气的预报也有重要意义。