Laming J Martin, Vourlidas Angelos, Korendyke Clarence, Chua Damien, Cranmer Steven R, Ko Yuan-Kuen, Kuroda Natsuha, Provornikova Elena, Raymond John C, Raouafi Nour-Eddine, Strachan Leonard, Tun-Beltran Samuel, Weberg Micah, Wood Brian E
Space Science Division, Code 7684, Naval Research Laboratory, Washington, DC 20375, USA.
Johns Hopkins University Applied Physics Laboratory, Laurel. MD 20723, USA.
Astrophys J. 2019 Jul 10;879(2):124. doi: 10.3847/1538-4357/ab23f1. Epub 2019 Jul 15.
We examine the different element abundances exhibited by the closed loop solar corona and the slow speed solar wind. Both are subject to the first ionization potential (FIP) effect, the enhancement in coronal abundance of elements with FIP below 10 eV (e.g., Mg, Si, Fe) with respect to high-FIP elements (e.g., O, Ne, Ar), but with subtle differences. Intermediate elements, S, P, and C, with FIP just above 10 eV, behave as high-FIP elements in closed loops, but are fractionated more like low-FIP elements in the solar wind. On the basis of FIP fractionation by the ponderomotive force in the chromosphere, we discuss fractionation scenarios where this difference might originate. Fractionation low in the chromosphere where hydrogen is neutral enhances the S, P, and C abundances. This arises with nonresonant waves, which are ubiquitous in open field regions, and is also stronger with torsional Alfvén waves, as opposed to shear (i.e., planar) waves. We discuss the bearing these findings have on models of interchange reconnection as the source of the slow speed solar wind. The outflowing solar wind must ultimately be a mixture of the plasma in the originally open and closed fields, and the proportions and degree of mixing should depend on details of the reconnection process. We also describe novel diagnostics in ultraviolet and extreme ultraviolet spectroscopy now available with these new insights, with the prospect of investigating slow speed solar wind origins and the contribution of interchange reconnection by remote sensing.
我们研究了闭环日冕和低速太阳风所呈现的不同元素丰度。两者都受到第一电离势（FIP）效应的影响，即FIP低于10电子伏特的元素（如Mg、Si、Fe）在日冕中的丰度相对于高FIP元素（如O、Ne、Ar）有所增强，但存在细微差异。FIP略高于10电子伏特的中间元素S、P和C在闭环中表现为高FIP元素，但在太阳风中的分馏更类似于低FIP元素。基于色球层中 ponderomotive 力引起的FIP分馏，我们讨论了这种差异可能产生的分馏情形。色球层中氢呈中性时的低分馏增强了S、P和C的丰度。这是由非共振波引起的，非共振波在开放磁场区域普遍存在，并且与剪切（即平面）波相比，扭转阿尔文波引起的这种现象更强。我们讨论了这些发现对作为低速太阳风来源的交换重联模型的影响。外流的太阳风最终必定是原本开放和封闭磁场中等离子体的混合，混合的比例和程度应取决于重联过程的细节。我们还描述了基于这些新见解现有的紫外和极紫外光谱学中的新型诊断方法，有望通过遥感研究低速太阳风的起源以及交换重联的贡献。
