标题： 日冕物质抛射通量绳在爆发过程中环面磁通量的演化 显示英文标题

标题： Evolution of the Toroidal Flux of CME Flux Ropes during Eruption

摘要： 日冕物质抛射（CMEs）是日冕磁场的大规模爆炸。 人们认为，在爆发过程中，磁重联显著构建了CME的核心结构——磁通量绳。 然而，通量绳的定量演化，特别是其环向通量，仍然不清楚。 在本文中，我们研究了四个事件中CME通量绳的环向通量的演化。 环向通量被估计为通量绳足点区域的磁通量，该区域通过一种同时考虑日冕暗化和耀斑条带钩状结构的方法来识别。 我们发现，所有四个事件中CME通量绳的环向通量表现出两阶段演化：一个快速增加阶段随后是一个减少阶段。 我们进一步将环向通量的演化与地球静止轨道环境卫星的软X射线通量的演化进行了比较，发现它们在时间上基本同步，只是前者峰值略有延迟。 结果表明，CME通量绳的环向通量可能首先由主要发生在剪切的上部场中的重联快速构建，然后由通量绳内部扭曲场线之间的重联减少，这一结论得到了最近一项CME三维磁流体动力学模拟的启示。 显示英文摘要

摘要： Coronal mass ejections (CMEs) are large-scale explosions of the coronal magnetic field. It is believed that magnetic reconnection significantly builds up the core structure of CMEs, a magnetic flux rope, during the eruption. However, the quantitative evolution of the flux rope, particularly its toroidal flux, is still unclear. In this paper, we study the evolution of the toroidal flux of the CME flux rope for four events. The toroidal flux is estimated as the magnetic flux in the footpoint region of the flux rope, which is identified by a method that simultaneously takes the coronal dimming and the hook of the flare ribbon into account. We find that the toroidal flux of the CME flux rope for all four events shows a two-phase evolution: a rapid increasing phase followed by a decreasing phase. We further compare the evolution of the toroidal flux with that of the Geostationary Operational Environmental Satellites soft X-ray flux and find that they are basically synchronous in time, except that the peak of the former is somewhat delayed. The results suggest that the toroidal flux of the CME flux rope may be first quickly built up by the reconnection mainly taking place in the sheared overlying field and then reduced by the reconnection among the twisted field lines within the flux rope, as enlightened by a recent 3D magnetohydrodynamic simulation of CMEs.