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首页> 外文期刊>Journal of Geophysical Research, A. Space Physics: JGR >Neutral H_2 and H_2~+ ions in the Saturnian magnetosphere
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Neutral H_2 and H_2~+ ions in the Saturnian magnetosphere

机译：中性H_2和H_2 ~ +离子的土星卫星磁气圈

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The Saturnian system is immersed in an extended cloud of neutrals. Although water vapor ejected from Enceladus' south pole is the dominant neutral source, photolysis and radiolysis of ices can release H_2O, O_2, and H_2 from the icy ring particles and the icy satellites, and Titan's atmosphere is a source of H_2. Once ionized, these neutrals are the source of the observed magnetospheric plasma. To understand the H_2~+ ion densities observed by the Cassini plasma spectrometer (CAPS), we developed a Monte Carlo test particle model to simulate the spatial morphology of the neutral H_2 cloud and the resulting H_2~+ ion source rates. The H2 lifetime is constrained by its local chemistry, which is computed from the latest plasma measurements by Cassini CAPS data. The main rings, Enceladus' water torus, Rhea, and Titan are considered as the primary sources of H_2 in our model. It is seen that H_2 accumulates over Saturn's main rings because of thermal accommodation with the ring particles, and Titan is the dominant source of H_2 in the outer magnetosphere (>～6 Rs). From ～6 to ～2.5 Rs, photodissociation of water from Enceladus and H_2 scattered from the ring atmosphere are comparable sources. The newly formed H_2~+ ions are lost by collisions with the ring particles inside ～2.5 R_S, by interchange processes in the middle magnetosphere, and by flow down the tail in the outer magnetosphere. The density distribution of H_2~+ estimated from our ion source rates roughly agrees with CAPS observations, and we show that the H_2~+ density near the equator over the main rings is at least 1 order of magnitude smaller than O_2~+, possibly consistent with the nondetection of H_2~+ by CAPS at Saturn orbit insertion.
机译：土星的系统是沉浸在一个扩展中性色的云。从土卫二的南极是占主导地位的中性的来源、光解和冰的辐解可以释放H_2O、成分和H_2从冰冷的戒指吗粒子和冰冷的卫星,土卫六大气是H_2的来源。这些中性色是观察到的来源磁性层的等离子体。由卡西尼号等离子体离子密度观测光谱仪(帽),我们开发了一个蒙特卡洛测试粒子模型来模拟空间形态学的中立云和H_2结果H_2 ~ +离子源。受到当地化学,这是从最新的计算等离子体测量卡西尼帽数据。水环,土卫五,并视为泰坦在我们的模型中H_2的主要来源。看到H_2积累在土星的主因为热住宿的戒指环粒子,泰坦是主要来源外磁气圈的H_2 (> ~ 6 Rs)。~ 6 ~ 2.5 Rs,光离解的水土卫二和H_2分散的戒指大气具有可比性。形成H_2 ~ +离子失去了通过碰撞~ 2.5 R_S内部环粒子,通过交换过程中磁层,流外磁气圈的尾巴。H_2 ~ +估计的密度分布我们的离子源利率大致同意帽观察,我们表明,H_2 ~ +密度赤道附近至少在主环1个数量级小于成分~ +,可能符合nondetection H_2 ~ +的帽子在土星轨道插入。

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