Baker Deborah, Janvier Miho, Démoulin Pascal, Mandrini Cristina H
1Mullard Space Science Laboratory, University College London, Holmbury, St. Mary, Dorking, Surrey, KT22 9XF UK.
2Institut d'Astrophysique Spatiale, CNRS, Univ. Paris-Sud, Université Paris-Saclay, Bât. 121, 91405 Orsay cedex, France.
Sol Phys. 2017;292(4):46. doi: 10.1007/s11207-017-1072-9. Epub 2017 Mar 22.
We analyze the evolution of Fe xii coronal plasma upflows from the edges of ten active regions (ARs) as they cross the solar disk using the (EIS) to do this. Confirming the results of Démoulin ( , 341, 2013), we find that for each AR there is an observed long-term evolution of the upflows. This evolution is largely due to the solar rotation that progressively changes the viewpoint of dominantly stationary upflows. From this projection effect, we estimate the unprojected upflow velocity and its inclination to the local vertical. AR upflows typically fan away from the AR core by 40° to nearly vertical for the following polarity. The span of inclination angles is more spread out for the leading polarity, with flows angled from -29° (inclined toward the AR center) to 28° (directed away from the AR). In addition to the limb-to-limb apparent evolution, we identify an intrinsic evolution of the upflows that is due to coronal activity, which is AR dependent. Furthermore, line widths are correlated with Doppler velocities only for the few ARs with the highest velocities. We conclude that for the line widths to be affected by the solar rotation, the spatial gradient of the upflow velocities must be large enough such that the line broadening exceeds the thermal line width of Fe xii. Finally, we find that upflows occurring in pairs or multiple pairs are a common feature of ARs observed by /EIS, with up to four pairs present in AR 11575. This is important for constraining the upflow-driving mechanism as it implies that the mechanism is not local and does not occur over a single polarity. AR upflows originating from reconnection along quasi-separatrix layers between overpressure AR loops and neighboring underpressure loops is consistent with upflows occurring in pairs, unlike other proposed mechanisms that act locally in one polarity.
The online version of this article (doi:10.1007/s11207-017-1072-9) contains supplementary material, which is available to authorized users.
我们利用日地关系天文台（EIS）分析了十个活动区（ARs）边缘的铁十二（Fe xii）日冕等离子体向上流动在穿越太阳圆盘时的演化情况。证实了德穆兰（Démoulin，2013年，第341页）的结果，我们发现每个活动区的向上流动都有一个观测到的长期演化。这种演化在很大程度上是由于太阳自转，它逐渐改变了主要静止向上流动的观测视角。基于这种投影效应，我们估计了未投影的向上流动速度及其相对于局部垂直方向的倾角。活动区的向上流动通常从活动区核心向外散开40°，对于后续极性而言接近垂直。对于前导极性，倾角范围分布更广，流动角度从-29°（朝向活动区中心倾斜）到28°（背离活动区）。除了从边缘到边缘的明显演化外，我们还识别出向上流动的一种内在演化，这是由于日冕活动引起的，且依赖于活动区。此外，只有少数速度最高的活动区，线宽才与多普勒速度相关。我们得出结论，为了使线宽受到太阳自转的影响，向上流动速度的空间梯度必须足够大，以使线展宽超过铁十二的热谱线宽度。最后，我们发现成对或多对出现的向上流动是日地关系天文台（EIS）观测到的活动区的一个常见特征，在活动区11575中最多有四对。这对于限制向上流动驱动机制很重要，因为这意味着该机制不是局部的，也不是在单一极性上发生的。与其他在一个极性上局部起作用的提出机制不同，源自超压活动区回路和相邻欠压回路之间准分离层重联的活动区向上流动与成对出现的向上流动是一致的。
本文的在线版本（doi:10.1007/s11207-017-1072-9）包含补充材料，授权用户可以获取。
