Enceladus : A potential source of ammonia products and molecular nitrogen for Saturn's magnetosphere
Enceladus : A potential source of ammonia products and molecular nitrogen for Saturn's magnetosphere
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土卫二：土星磁层氨产品和分子氮的潜在来源
DOI：
10.1029/2008ja013352
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发表时间：
2008
影响因子：
--
通讯作者：
D. Young
中科院分区：
文献类型：
--
作者：
H. Smith;H. Smith;M. Shappirio;Robert E. Johnson;D. Reisenfeld;E. Sittler;F. Crary;D. McComas;D. Young
原则上，在土星磁层中探测到氮可以为其卫星和脆弱环的起源和演化提供线索。Smith等人（2005）首次使用卡西尼等离子体光谱仪（CAPS）发现了低能N+。N+主要出现在土星的内磁层（< ~ 14 Rs），表明土卫二的氮源而不是预期的土卫六的氮源。但母体分子种类尚未确定。随后的模型表明，土卫二上一个与离子中性质谱仪观测结果一致的小氮气源可以产生观测到的N+的空间分布。考虑到了解土卫二羽流的重要性，确定观测到的N+ （N2或NHx）的分子母体可以为土卫二的地下组成和产生羽流活动的过程提供线索。在本文中，我们扩展了Smith等人（2007）的工作，以确定在土星内磁层中检测到的氮离子的源分子。我们对所有可用的CAPS数据进行了广泛的研究，以确定N2+或氨是否是这些氮离子的母分子。我们提供了检测产物离子（NHx+）的证据，可能来自氨，并提供了内磁层等离子体中可能存在的N2+量的上限。
[1] The detection of nitrogen species in Saturn's magnetosphere could, in principle, provide clues to the origin and evolution of its satellites and tenuous rings. Smith et al. (2005) first identified low-energy N+ using the Cassini Plasma Spectrometer (CAPS). N+ was predominantly seen in the Saturn's inner magnetosphere (<∼14 Rs), indicating an Enceladus nitrogen source rather than the expected Titan source. However, the parent molecular species was not confirmed. Subsequent modeling showed that a small N2 source at Enceladus consistent with ion neutral mass spectrometer observations could produce the observed spatial distribution of N+. Considering the significance of understanding the Enceladus plumes, identifying the molecular parent for the observed N+ (N2 or NHx) can provide clues to the subsurface composition of Enceladus and the processes generating this plume activity. In this paper, we expand on the work of Smith et al. (2007) to identify the source molecules for nitrogen ions detected in Saturn's inner magnetosphere. We conduct an extensive study of all available CAPS data to determine if N2+ or ammonia is the parent molecule for these nitrogen ions. We present evidence for the detection of product ions (NHx+), likely from ammonia, and provide upper limits on the amount of N2+ that may be present in the plasma in the inner magnetosphere.