Kuroda Natsuha, Laming J Martin
University Corporation for Atmospheric Research PO Box 3000 Boulder, CO 80307-3000, USA.
Space Science Division, Code 7684, Naval Research Laboratory, Washington DC 20375, USA.
Astrophys J. 2020 May 20;895(1). doi: 10.3847/1538-4357/ab8870. Epub 2020 May 21.
We present an examination of the first ionization potential (FIP) fractionation scenario, invoking the ponderomotive force in the chromosphere and its implications for the source(s) of slow-speed solar winds by using observations from The Advanced Composition Explorer (ACE). Following a recent conjecture that the abundance enhancements of intermediate FIP elements, S, P, and C, in slow solar winds can be explained by the release of plasma fractionated on open fields, though from regions of stronger magnetic field than usually associated with fast solar wind source regions, we identify a period in 2008 containing four solar rotation cycles that show repeated pattern of sulfur abundance enhancement corresponding to a decrease in solar wind speed. We identify the source regions of these slow winds in global magnetic field models, and find that they lie at the boundaries between a coronal hole and its adjacent active region, with origins in both closed and open initial field configurations. Based on magnetic field extrapolations, we model the fractionation and compare our results with element abundances measured by ACE to estimate the solar wind contributions from open and closed fields, and to highlight potentially useful directions for further work.
我们利用先进成分探测器（ACE）的观测结果，对首次电离势（FIP）分馏情景进行了研究，探讨了色球层中的有质动力及其对低速太阳风源的影响。最近有一个猜想，即慢速太阳风中中等FIP元素（硫、磷和碳）的丰度增加可以通过开放磁场中分离出的等离子体的释放来解释，尽管这些区域的磁场比通常与快速太阳风源区域相关的磁场更强。我们确定了2008年包含四个太阳自转周期的一段时间，这段时间显示出硫丰度增加与太阳风速度降低相对应的重复模式。我们在全球磁场模型中确定了这些慢速风的源区，发现它们位于日冕洞与其相邻活动区之间的边界处，起源于封闭和开放的初始磁场构型。基于磁场外推，我们对分馏进行了建模，并将我们的结果与ACE测量的元素丰度进行比较，以估计开放和封闭磁场对太阳风的贡献，并突出进一步工作可能有用的方向。
