太阳离临线廓线对电子密度分层和速度分布各向异性的敏感性
Sensitivity of solar off-limb line profiles to electron density stratification and the velocity distribution anisotropy
摘要：
本文研究了电子密度分层对日冕洞中H I Ly- $α$线和O VI、Mg X双重线强度分布的影响。我们采用了一个分析的2-D模型的大规模日冕磁场，提供了一个很好的代表性的日冕在最低限度的太阳活动。我们使用质量通量守恒方程来确定太阳风在日冕中的任何位置的流出速度，并考虑到沿视线（LOS）的积分。我们所做的主要假设是，没有考虑日冕物质的动力学温度的各向异性。我们发现，在距离大于1 Rsun从太阳表面的O VI和Mg X的发射线的宽度是敏感的细节所采用的电子密度分层。然而，纯辐射线Ly- $α$几乎不受影响。计算的总强度的Ly- $α$和O VI双峰依赖于密度分层的程度较低，并与所观察到的大多数考虑的密度模型。所观察到的配置文件的Ly- $α$和Mg X的宽度很好地再现了大多数考虑的电子密度分层，而对于O VI的双重只有少数分层给出令人满意的结果。由SOHO资料推导出的密度结果得到的O-VI剖面的宽度和强度比与UNOPS观测到的值比较接近，尽管只采用了各向同性的速度分布。这些密度分布也再现了其他被认为具有良好精度的观测。因此，需要一个强的各向异性的速度分布（即温度各向异性）是不那么明确的，因为以前的调查的UNODC数据建议。...
英文摘要：
The effect of the electron density stratification on the intensity profiles of the H I Ly-$α$ line and the O VI and Mg X doublets formed in solar coronal holes is investigated. We employ an analytical 2-D model of the large scale coronal magnetic field that provides a good representation of the corona at the minimum of solar activity. We use the mass-flux conservation equation to determine the outflow speed of the solar wind at any location in the solar corona and take into account the integration along the line of sight (LOS). The main assumption we make is that no anisotropy in the kinetic temperature of the coronal species is considered. We find that at distances greater than 1 Rsun from the solar surface the widths of the emitted lines of O VI and Mg X are sensitive to the details of the adopted electron density stratification. However, Ly-$α$, which is a pure radiative line, is hardly affected. The calculated total intensities of Ly-$α$ and the O VI doublet depend to a lesser degree on the density stratification and are comparable to the observed ones for most of the considered density models. The widths of the observed profiles of Ly-$α$ and Mg X are well reproduced by most of the considered electron density stratifications, while for the O VI doublet only few stratifications give satisfying results. The densities deduced from SOHO data result in O VI profiles whose widths and intensity ratio are relatively close to the values observed by UVCS although only isotropic velocity distributions are employed. These density profiles also reproduce the other considered observables with good accuracy. Thus the need for a strong anisotropy of the velocity distribution (i.e. a temperature anisotropy) is not so clear cut as previous investigations of UVCS data suggested. ...
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