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首页> 外文期刊>Journal of Geophysical Research, A. Space Physics: JGR >Saturn’s dynamic magnetotail: A comprehensive magnetic field and plasma survey of plasmoids and traveling compression regions and their role in global magnetospheric dynamics
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Saturn’s dynamic magnetotail: A comprehensive magnetic field and plasma survey of plasmoids and traveling compression regions and their role in global magnetospheric dynamics

机译：土星的动态磁尾:全面磁场和等离子体等离子粒团和调查旅行压缩区域及其作用全球磁性层的动态

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We present a comprehensive study of the magnetic field and plasma signatures of reconnection events observed with the Cassini spacecraft during the tail orbits of 2006. We examine their “local” properties in terms of magnetic field reconfiguration and changing plasma flows. We also describe the “global” impact of reconnection in terms of the contribution to mass loss, flux closure, and large-scale tail structure. The signatures of 69 plasmoids, 17 traveling compression regions (TCRs), and 13 planetward moving structures have been found. The direction of motion is inferred from the sign of the change in the B_θ component of the magnetic field in the first instance and confirmed through plasma flow data where available. The plasmoids are interpreted as detached structures, observed by the spacecraft tailward of the reconnection site, and the TCRs are interpreted as the effects of the draping and compression of lobe magnetic field lines around passing plasmoids. We focus on the analysis and interpretation of the tailward moving (south-to-north field change) plasmoids and TCRs in this work, considering the planetward moving signatures only from the point of view of understanding the reconnection x-line position and recurrence rates. We discuss the location spread of the observations, showing that where spacecraft coverage is symmetric about midnight, reconnection signatures are observedmore frequently on the dawn flank than on the dusk flank. We show an example of a chain of two plasmoids and two TCRs over 3 hours and suggest that such a scenario is associated with a single-reconnection event, ejecting multiple successive plasmoids. Plasma data reveal that one of these plasmoids contains H+ at lower energy and W+ at higher energy, consistent with an inner magnetospheric source, and the total flow speed inside the plasmoid is estimated with an upper limit of 170 km/s. We probe the interior structure of plasmoids and find that the vastmajority of examples at Saturn show a localized decrease in fieldmagnitude as the spacecraft passes through the structure. We take the trajectory of Cassini into account, as, during 2006, the spacecraft’s largely equatorial position beneath the hinged current sheet meant that it rarely traversed the center of plasmoids. We present an innovative method of optimizing the window size for minimum variance analysis (MVA) and apply thisMVA across several plasmoids to explore their interior morphology in more detail, finding that Saturn’s tail contains both loop-like and flux rope-like plasmoids. We estimate the mass lost downtail through reconnection and suggest that the apparent imbalance between mass input and observed plasmoid ejection may mean that alternative mass lossmethods contribute to balancing Saturn’s mass budget. We also estimate the rate ofmagnetic flux closure in the tail and find that when open field line closure is active, it plays a very significant role in flux cycling at Saturn.
机译：我们提出一个全面的研究磁场和等离子体签名重新连接事件观察与卡西尼宇宙飞船在2006年的尾巴的轨道。“本地”属性的磁场重新配置和改变等离子体流。也描述了“全球”重新连接的影响质量损失,通量的贡献关闭,大规模尾结构。69等离子粒团的签名,17旅行压缩区域(tcr)和13 planetward移动的结构被发现。运动是推断的变化的迹象在B_θ组件的磁场第一个实例,证实了通过等离子体流数据可用。解释为分离的结构,观察到宇宙飞船tailward重新连接的网站,和tcr解释为的影响叶磁的隔音材料和压缩周围的电场线通过等离子粒团。tailward的分析和解释(针对字段变化)等离子粒团移动和识别工作,考虑到planetward仅从的角度移动的签名了解重新连接x轴的位置和复发率。传播的观察,表明在哪里宇宙飞船的覆盖是对称的午夜,重新连接签名observedmore经常在黎明侧面而不是黄昏侧面。等离子粒团,两个细胞/ 3小时和建议这样的场景是关联到一个single-reconnection事件,将多个连续的等离子粒团。这些等离子粒团包含H +在较低的能量和W +在更高的能量,与一种内在一致磁性层的来源,总流的速度在等离子粒团估计上170 km / s的极限。结构的等离子粒团和发现在土星显示绝大多数的例子本地化在fieldmagnitude降低宇宙飞船穿过结构。卡西尼号的轨道,,在2006年,航天器的赤道位置在铰链电流片的意思它很少穿过等离子粒团的中心。我们提出一个创新的优化方法窗口大小为最小方差分析(MVA)并应用thisMVA跨多个等离子粒团更详细地探索其内部形态,发现土星的尾巴既包含环和通量绳子等离子粒团。估计质量损失downtail通过重新连接并显示明显不平衡质量的输入和观察等离子粒团弹射可能意味着选择质量lossmethods有助于平衡土星的质量预算。关闭的尾巴,发现当开放的领域行关闭活跃,它扮演了一个非常重要的角色在土星通量循环。

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