Cassini observations of ionospheric photoelectrons at large distances from Titan: Implications for Titan's exospheric environment and magnetic tail
Cassini observations of ionospheric photoelectrons at large distances from Titan: Implications for Titan's exospheric environment and magnetic tail
复制标题
DOI：
10.1029/2011ja017113
复制
发表时间：
2012-03
影响因子：
--
通讯作者：
A. Wellbrock;A. Coates;I. Sillanpää;G. Jones;C. Arridge;G. Lewis;D. Young;F. Crary;A. Aylward
中科院分区：
文献类型：
--
作者：
A. Wellbrock;A. Coates;I. Sillanpää;G. Jones;C. Arridge;G. Lewis;D. Young;F. Crary;A. Aylward
[1]卡西尼等离子体光谱仪（英语：Cassini Plasma Spectrometer）（CAPS）的电子光谱仪在土卫六的电离层中测量到24.1 eV附近的离散峰，并将其解释为光电子。这些光电子是由强太阳He II（30.4 nm）线电离N2产生的。它们通常在向阳面的电离层中被观测到，因为这是中性N2粒子可以被太阳辐射电离的地方。科茨等人（2007年）讨论了在T9遭遇期间土卫六遥远尾部的光电子的初步观测结果。在这里，我们描述了额外的光电子峰值观测距离土卫六，在那里他们不太可能起源于低中性N2密度。我们考虑在遭遇T15、T17和T40期间的尾部结构。我们推断，遥远的光电子可能已经通过磁连接从低海拔的向阳面电离层，在那里他们可能已经产生的观测站点。混合建模的结果支持这一想法。因此，光电子可能被用作磁场线的示踪剂，并进一步提高我们对土卫六复杂等离子体环境的理解。
[1] Discrete peaks near 24.1 eV are seen in electron spectra measured in Titan's ionosphere by the ELS (Electron Spectrometer), part of the Cassini Plasma Spectrometer (CAPS), and are interpreted as photoelectrons. These photoelectrons are generated as a result of ionization of N2 by the strong solar He II (30.4 nm) line. They are generally observed in the dayside ionosphere, because this is where neutral N2 particles can be ionized by solar radiation. Coates et al. (2007) discussed initial observations of photoelectrons in Titan's distant tail during the T9 encounter. Here, we describe additional photoelectron peak observations at large distances from Titan, where they are unlikely to have originated because of low neutral N2 densities. We consider the tail structures during the encounters T15, T17, and T40. We infer that the distant photoelectrons may have traveled to the observation sites by means of a magnetic connection from lower altitudes in the dayside ionosphere, where they could have been produced. This idea is supported by results of hybrid modeling. Thus photoelectrons may be used as tracers of magnetic field lines and further improve our understanding of Titan's complex plasma environment.