日冕物质抛射(CME)是造成地球空间非重现性地磁暴的主要来源，但并非所有的正面（朝向地球面）CME事件都能传播到地球空间。CME角宽度，即CME相对日心的张角，是影响它能否传播到地球的重要因素之一。已有研究表明，CME角宽度和其源区的某些太阳活动参数(活动区面积、磁通量、中性线长度、伴随耀斑/日珥参数等)之间具有一定的相关性，但相关系数不高，缺乏相应的定量关系研究。鉴于此，本项目将针对2010-2013年期间发生的对地CME事件，利用STEREO、SOHO卫星的多视角成像观测，配合行星际闪烁观测，研究CME真实的角宽度，同时用SDO、Hinode等高分辨率的卫星观测以及地面观测，分析这类CME事件的源区特征参数；进而在分类情况下研究CME真实角宽度与源区特征参数之间的相关关系和关联机制，基于统计结果建立相应的定量关系。项目研究成果可用于单卫星观测下CME角宽度的快速诊断。

Coronal mass ejections (CMEs) are the main source of the non-recurrent geomagnetic storms. However, not all the frontside CMEs (happening on the side facing the Earth) could encounter the geospace. The CME angular width, i.e., the angular span of the CME relative to the Sun center, is one of the most important factors that contribute to the probability of CME's encountering the Earth. Previous studies have demonstrated that the angular width of the CME is correlated with some of the solar activity parameters in the source region of the CME (such as: area and flux of the active region, length of the neutral line, parameters of the associated flare/filament). But the correlation coefficients are not high enough to give the quantitative prediction of the CME angular width. Therefore, this proposal is focused on the frontside CMEs happenning during 2010-2013. The coronagraph observations of STEREO and SOHO from different oberving directions will be used together with the IPS observations to study the true angular width of the CME. While, the high resolution data from SDO and Hinode as well as the ground-based observations will be used to analyse the characteristic parameters in the source region of the CME. Then the correlation relation and related mechanism between the angular width and the source region characteristic parameters of the CME will be investigated after deviding the CMEs into different catagories. The quantitative relation between the CME angular width and the characteristic parameters in its source region will be given based on the statistical results. The outcome of this proposal could be used in the fast diagnosing of the angular width of the CME based on its single spacecraft observations.