扩展日冕中氧离子优先加热和加速的改进约束
Improved Constraints on the Preferential Heating and Acceleration of Oxygen Ions in the Extended Solar Corona
摘要：
我们提出了一个详细的分析，在扩展的太阳日冕中的氧离子速度分布，与SOHO航天器上的紫外线日冕光谱仪（UNOPS）的观测的基础上。极冕洞在太阳活动极小期时会呈现出宽线宽和不寻常的O VI 1032、1037双谱线强度比。对这些特征的传统解释是氧离子具有很强的温度各向异性，垂直于磁场的温度远大于平行于磁场的温度。然而，最近的工作由Raouvillas和Solanki建议，这可能是可能的模型的观测使用各向同性的速度分布。在本文中，我们分析了一个扩展的数据集，表明各向异性分布的原始解释是唯一一个完全符合观察。有必要搜索离子等离子体参数的全范围，以确定与Udash数据一致的概率最高的值。导出的离子流出速度和垂直的动力学温度与早期的结果是一致的，并继续有强有力的证据优先离子加热和加速相对于氢。在2.1太阳半径以上的日心高度，每一个Udash数据点是更符合各向异性分布比各向同性分布。在3个太阳半径以上的高度，各向同性的确切概率取决于电子密度选择模拟的视线分布的O VI发射率。（摘要摘录）
英文摘要：
We present a detailed analysis of oxygen ion velocity distributions in the extended solar corona, based on observations made with the Ultraviolet Coronagraph Spectrometer (UVCS) on the SOHO spacecraft. Polar coronal holes at solar minimum are known to exhibit broad line widths and unusual intensity ratios of the O VI 1032, 1037 emission line doublet. The traditional interpretation of these features has been that oxygen ions have a strong temperature anisotropy, with the temperature perpendicular to the magnetic field being much larger than the temperature parallel to the field. However, recent work by Raouafi and Solanki suggested that it may be possible to model the observations using an isotropic velocity distribution. In this paper we analyze an expanded data set to show that the original interpretation of an anisotropic distribution is the only one that is fully consistent with the observations. It is necessary to search the full range of ion plasma parameters to determine the values with the highest probability of agreement with the UVCS data. The derived ion outflow speeds and perpendicular kinetic temperatures are consistent with earlier results, and there continues to be strong evidence for preferential ion heating and acceleration with respect to hydrogen. At heliocentric heights above 2.1 solar radii, every UVCS data point is more consistent with an anisotropic distribution than with an isotropic distribution. At heights above 3 solar radii, the exact probability of isotropy depends on the electron density chosen to simulate the line-of-sight distribution of O VI emissivity. (abridged abstract)
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