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首页> 外文期刊>The Astrophysical journal >OBSERVATIONS OF CORE FALLBACK DURING CORONAL MASS EJECTIONS
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OBSERVATIONS OF CORE FALLBACK DURING CORONAL MASS EJECTIONS

机译：冠状大肠切除术中骨质返流的观察

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摘要

White-light observations made with the Large Angle and Spectrometric Coronagraph (LASCO) during the present solar maximum have revealed a multitude of faint, inward-moving features at heliocentric distances of r～2-6 solar radius. Most of these structures appear to originate above r～3 solar radius and may be signatures of the closing-down of magnetic flux at the boundaries of coronal holes or in the aftermath of coronal mass ejections (CMEs). Here, we present observations of a different type of inflow, in which material within the bright core of a CME collapses back toward the Sun after rising to heights of r～2.5-6 solar radius. We have identified roughly 20 such fallback events during 1998-2001. The core structures, which have the form of loops or concave-outward flux ropes, ascend into the coronagraph field of view beyond 2 solar radius with speeds of ～100-400 km s~(-1) but return with speeds of only ～50-200 km s~(-1). The initial deceleration rates of ~20-100 ms~(-2) are comparable to the local gravitational deceleration G solar mass/r~2 but continually decrease with time. The associated CMEs tend to be impulsive but relatively slow, with the leading front moving outward at ～250-450 km s~(-1) and often showing some deceleration. It is thus not surprising that some fraction of the core material fails to reach escape speeds, remaining bound to the Sun by gravitational and magnetic tension forces. We suggest that the dynamical behavior of the core may be determined in part by momentum exchanges with the background medium, which consists of ongoing outflows of CME material, ambient solar wind, and inflow streams. In particular, we attribute the asymmetry of the up-down trajectories to the action of such drag forces, whose direction changes from inward to outward as the core decelerates.
机译：在当前太阳最大时用大角度和光谱日冕仪（LASCO）进行的白光观测显示，在太阳半径r〜2-6的日心距离上有许多微弱的向内移动特征。这些结构中的大多数似乎起源于r〜3太阳半径以上，并且可能是在日冕孔边界处或日冕物质抛射（CME）之后磁通封闭的标志。在这里，我们提出了另一种流入类型的观测结果，其中CME明亮核内的物质在上升到r〜2.5-6太阳半径的高度后向太阳塌陷。我们已经确定了1998-2001年间大约有20种此类后备事件。呈环状或向外凹入的通量绳形式的核心结构，以〜100-400 km s〜（-1）的速度上升到日冕图视场之外，速度超过2个太阳半径，但以〜50的速度返回-200公里s〜（-1）。 〜20-100 ms〜（-2）的初始减速率与局部重力减速G太阳质量/ r〜2相当，但随着时间不断减小。相关的CME趋向于冲动，但相对较慢，前锋在〜250-450 km s〜（-1）处向外移动，并经常表现出一定的减速。因此，不足为奇的是，芯材的某些部分无法达到逃逸速度，而在重力和磁力的作用下仍然与太阳结合。我们建议，岩心的动力学行为可能部分取决于与背景介质的动量交换，该介质由持续不断的CME材料流出，环境太阳风和流入流组成。尤其是，我们将上下轨迹的不对称性归因于这种拖曳力的作用，随着核心的减速，其拖曳力的方向从内向外变化。

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