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arXiv 2007.13180astro-ph.SR
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极冕洞中质子和电子的加热率:来自紫外日冕光谱仪的经验约束

Heating Rates for Protons and Electrons in Polar Coronal Holes: Empirical Constraints from the Ultraviolet Coronagraph Spectrometer

Steven R. Cranmer

摘要:

扩展日冕的紫外光谱是测量加速太阳风中质子、电子和重离子性质的有力工具。在太阳活动极小期,从南北两极向上扩展的大冕洞是低密度的无碰撞区域,在那里可以检测到偏离单流体热平衡的情况。这些偏离的准确表征有助于确定最终负责日冕加热的动力学过程。本文分析了紫外日冕光谱仪对H I Lyman α线的测量结果,给出了太阳风速度、电子密度、电子温度、质子温度(平行于和垂直于磁场方向)和阿尔芬波振幅的约束值。分析过程包括创建一个大型的随机经验模型集合,模拟其Lyman α分布,并仅为与Udash数据一致的模型构建后验概率分布。由此产生的温度并没有表现出很大的径向变化之间的日心距离1.4和4太阳半径。电子、平行质子和垂直质子温度的典型值分别为1.2、1.8和1.9 MK。结果值的“非热”阿尔芬波振幅显示弱耗散的证据,与总能量损失率,以及同意与独立推导的总加热速率的质子和电子。适度的阿尔芬波振幅似乎解决了一些紧张的文献之间的竞争索赔更高(无阻尼)和更低(重阻尼)的价值。

英文摘要:

Ultraviolet spectroscopy of the extended solar corona is a powerful tool for measuring the properties of protons, electrons, and heavy ions in the accelerating solar wind. The large coronal holes that expand up from the north and south poles at solar minimum are low-density collisionless regions in which it is possible to detect departures from one-fluid thermal equilibrium. An accurate characterization of these departures is helpful in identifying the kinetic processes ultimately responsible for coronal heating. In this paper, Ultraviolet Coronagraph Spectrometer (UVCS) measurements of the H I Lyman alpha line are analyzed to constrain values for the solar wind speed, electron density, electron temperature, proton temperature (parallel and perpendicular to the magnetic field) and Alfven-wave amplitude. The analysis procedure involves creating a large randomized ensemble of empirical models, simulating their Lyman alpha profiles, and building posterior probability distributions for only the models that agree with the UVCS data. The resulting temperatures do not exhibit a great deal of radial variation between heliocentric distances of 1.4 and 4 solar radii. Typical values for the electron, parallel proton, and perpendicular proton temperatures are 1.2, 1.8, and 1.9 MK, respectively. Resulting values for the "nonthermal" Alfven wave amplitude show evidence for weak dissipation, with a total energy-loss rate that agrees well with an independently derived total heating rate for the protons and electrons. The moderate Alfven-wave amplitudes appear to resolve some tension in the literature between competing claims of both higher (undamped) and lower (heavily damped) values.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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