Abstract NASA's Genesis Mission returned solar wind (SW) to the Earth for analysis to derive the composition of the solar photosphere from solar material. SW analyses control the precision of the derived solar compositions, but their ultimate accuracy is limited by the theoretical or empirical models of fractionation due to SW formation. Mg isotopes are “ground truth” for these models since, except for CAIs, planetary materials have a uniform Mg isotopic composition (within ≤1‰) so any significant isotopic fractionation of SW Mg is primarily that of SW formation and subsequent acceleration through the corona. This study analyzed Mg isotopes in a bulk SW diamond‐like carbon (DLC) film on silicon collector returned by the Genesis Mission. A novel data reduction technique was required to account for variable ion yield and instrumental mass fractionation (IMF) in the DLC. The resulting SW Mg fractionation relative to the DSM‐3 laboratory standard was (−14.4‰, −30.2‰) ± (4.1‰, 5.5‰), where the uncertainty is 2ơ SE of the data combined with a 2.5‰ (total) error in the IMF determination. Two of the SW fractionation models considered generally agreed with our data. Their possible ramifications are discussed for O isotopes based on the CAI nebular composition of McKeegan et al. (2011).

中文翻译：

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来自类金刚石碳膜的大量太阳风的镁同位素

摘要 美国宇航局的创世纪任务将太阳风 (SW) 返回地球进行分析，以从太阳物质中得出太阳光球层的成分。SW 分析控制所得出的太阳成分的精度，但其最终精度受到 SW 形成引起的分馏理论或经验模型的限制。镁同位素是这些模型的“基本事实”，因为除 CAI 外，行星材料具有均匀的镁同位素组成（≤1‰），因此任何显着的 SW Mg 同位素分馏主要是 SW 形成和随后通过日冕加速的同位素分馏。这项研究分析了创世纪任务返回的硅收集器上的块状 SW 类金刚石碳 (DLC) 薄膜中的镁同位素。需要一种新颖的数据缩减技术来解释 DLC 中的可变离子产率和仪器质量分级 (IMF)。相对于 DSM-3 实验室标准，所得 SW Mg 分馏为 (−14.4‰，−30.2‰) ± (4.1‰，5.5‰)，其中不确定度为数据的 2ơ SE 与 2.5‰（总）误差相结合在国际货币基金组织的决定中。两个 SW 分馏模型总体上与我们的数据一致。基于 McKeegan 等人的 CAI 星云组成，讨论了它们对 O 同位素的可能影响。（2011）。