基于成像和光谱观测的三维磁重联研究

Solar flares and flux rope eruptions are thought to be the main drivers of space weather, and the study of this field also helps to interpret the stellar flares, for which observations remain limited. Recently abundant observational data show that the traditional 2D flare model has limitations, and it needs people to acquire the intrinsic 3D observational features of flares, in order to develop and consummate the 3D flare models. Our research mainly focuses on: (1) statistic study of big flares using three-viewpoints’ observations: based on the almost 7 years’ multi-viewpoint observations of the SDO and STEREO, we statistically study the 3D characteristics during the process of flares, including the complex morphology and evolution of flare ribbons and slipping motions of flare loops. (2) study of the typical events using the imaging and spectroscopic observations: based on the IRIS and high-resolution observations of the NVST, we study the typical flare events in detail, analyze the plasma evolution at different temperatures and mass flows during the process of 3D magnetic reconnections. (3) comprehensive study combining the multi-wavelength observations with 3D magnetic field extrapolation: extrapolate the 3D magnetic topology at the source region of eruptions, analyze the locations and magnetic configuration of magnetic reconnection. By using the new, abundant and high-quality observations, we try to reveal the features of 3D magnetic reconnection and its interrelated mechanism with solar flares and flux rope eruptions, in order to develop and consummate the 3D flare models.

太阳耀斑和磁绳爆发被认为是空间天气的主要驱动源，该领域的研究也帮助人们认识观测受限的恒星耀斑。近期丰富的观测表明传统的两维耀斑模型具有局限性，亟需人们认识耀斑内禀的三维观测特征，以发展和完善三维的耀斑模型。本项目主要研究：（1）三视角观测大耀斑的统计研究：基于SDO和STEREO卫星近七年的多视角观测数据，统计研究耀斑过程中的三维特征，包括耀斑带的复杂形态及演化、耀斑环的滑动运动等；（2）成像与光谱观测完备的典型事件研究：基于IRIS卫星和国内NVST高分辨率的观测，对典型耀斑事件进行详细的个例研究，分析三维磁重联过程中不同温度等离子体的演化、物质流动等；（3）多波段观测与三维磁场外推的综合研究：外推爆发活动源区的三维磁拓扑结构，分析磁重联发生位置和磁场位形。力争利用最新丰富优质的观测资料，揭示三维磁重联特性及其与耀斑和磁绳爆发的关联机制，理解太阳爆发活动的本质。

四年间，经过项目组各成员的共同努力，目前已顺利完成项目研究内容，实现既定的科学目标。在国际核心刊物上发表论文28篇，其中部分研究成果处于国际领先水平。取得的主要成果包括：（1）提出两类束缚耀斑的概念：一类耀斑表现出滑动磁重联、强的剪切和稳定的暗条；二类耀斑伴随暗条的失败爆发，被耀斑上方的强磁场所约束。揭示出耀斑束缚的一种新机制—复杂磁拓扑系统中的滑动磁重联过程。（2）基于SDO卫星近10年的观测，建立了目前最大的爆发和束缚耀斑样本库，发现活动区的总磁通量是决定大耀斑爆发属性的重要因素，耀斑-日冕物质抛射（CME）相关率与活动区的磁通量表现出很强的反相关。该发现为预报CME和空间灾害性天气提供了磁通量的定量标准，同时对理解恒星爆发活动具有一定的启示。（3）研究了圆形耀斑过程中罕见的两阶段能量释放过程,提出在“扇面-脊线”拓扑结构下，包含两组耀斑带和多暗条系统的复合爆发模型。取得的研究成果推进了人们对三维磁重联的特性、耀斑触发及束缚机制的认识，一方面对传统理论模型提出了新的挑战，同时也为进一步的理论和数值模拟研究提供了宝贵的实测依据。