UVCS/SOHO empirical determinations of anisotropic velocity distributions in the solar corona
UVCS/SOHO empirical determinations of anisotropic velocity distributions in the solar corona
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DOI：
10.1086/311434
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发表时间：
1998-07-01
影响因子：
4.9
通讯作者：
Suleiman, RM
中科院分区：
文献类型：
--
作者：
Kohl, JL;Noci, G;Suleiman, RM
根据太阳和日球层天文台紫外日冕谱仪的观测结果，提出了一个自洽的太阳极小期附近极日冕洞等离子体参数的经验模型。该模型描述了1996年11月至1997年4月期间电子、H-0和O5+密度的径向分布，以及H-0和O5+的流出速度和未确定的最可能速度。在这篇论文中，我们将H I Ly α和O VI λ λ 1032, 1037发射线的观测结果与等离子体参数的空间模型进行了比较，并迭代以获得测量量和合成观测量之间的最佳一致性。H-0原子和O5+离子在大多数半径处的出乎意料的大线宽是各向异性速度分布的结果，这与纯粹的热运动或热波和横波速度组合的预期运动不一致。在2 R以上，观测到的O5+的横向最可能速度明显大于H-0的相应运动，O5+的流出速度也明显大于H-0的相应速度。我们讨论了各种日冕加热和加速理论模型的限制和意义。
We present a self-consistent empirical model for several plasma parameters of a polar coronal hole near solar minimum, derived from observations with the Solar and Heliospheric Observatory Ultraviolet Coronagraph Spectrometer. The model describes the radial distribution of density for electrons, H-0, and O5+ and the outflow velocity and unresolved most probable velocities for H-0 and O5+ during the period between 1996 November and 1997 April. In this Letter, we compare observations of H I Ly alpha and O VI lambda lambda 1032, 1037 emission lines with spatial models of the plasma parameters, and we iterate for optimal consistency between measured and synthesized observable quantities. The unexpectedly large line widths of H-0 atoms and O5+ ions at most radii are the result of anisotropic velocity distributions, which are not consistent with purely thermal motions or the expected motions from a combination of thermal and transverse wave velocities. Above 2 R., the observed transverse, most probable speeds for O5+ are significantly larger than the corresponding motions for H-0, and the outflow velocities of O5+ are also significantly larger than the corresponding velocities of H-0. We discuss the constraints and implications on various theoretical models of coronal heating and acceleration.