Magnetospheric and Plasma Science with Cassini-Huygens
Magnetospheric and Plasma Science with Cassini-Huygens
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卡西尼-惠更斯号的磁层和等离子体科学
DOI：
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发表时间：
2002
期刊：
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通讯作者：
D. Young
中科院分区：
文献类型：
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作者：
M. Blanc;S. Bolton;J. Bradley;M. Burton;T. Cravens;I. Dandouras;M. Dougherty;M. Festou;J. Feynman;R. Johnson;T. Gombosi;W. Kurth;P. Liewer;B. Mauk;S. Maurice;D. Mitchell;F. Neubauer;J. Richardson;D. Shemansky;E. Sittler;B. Tsurutani;P. Zarka;L. Esposito;E. Grün;D. Gurnett;A. Kliore;S. M. Krimigis;D. Southwood;J. Waite;D. Young
土星的磁层和等离子体科学研究为深入探索两种类型的磁层提供了独特的机会。这些是泰坦与周围等离子体流和土星“固有”磁层相互作用产生的“感应”磁层，土星行星磁场在太阳风流内部产生的磁腔。将使用最先进和最多样化的仪器来探索这两个物体，以分析有史以来飞往行星的等离子体、高能粒子和场。这些仪器将能够处理和解决有关这两个磁层与其环境相互作用的一系列关键科学问题。由土卫六的大气层/电离层引起的障碍物周围的磁层等离子体流会产生一个细长的空腔和尾流，我们称之为“感应磁层”。这种相互作用的马赫数特征使其在太阳系中独一无二。我们首先描述土卫六的电离层，它是外部等离子体流的障碍。然后，我们研究土卫六的感应磁层、其结构、动力学和变异性，并讨论土卫六可能存在的小型固有磁场。然后描述土星磁层，它与土星环境中除土卫六外的所有其他组成部分进行动态和化学耦合。我们首先总结磁层等离子体和场的形态。然后我们讨论我们对每个区域磁层相互作用的了解。从最里面的区域开始向外移动，我们首先描述主环的区域及其与低纬度电离层的联系。接下来，产生特定磁层相互作用的冰卫星被嵌入相对密集的中性气体云中，该气体云也与扩散E环的空间范围重叠。该区域构成了灰尘、中性气体和等离子体群之间直接和相互耦合的非常有趣的例子。土星半径约十二个之外是外磁层，那里的动力学主要由其与太阳风和大型氢环面的耦合决定。它是磁层和土星高层大气之间强烈耦合的区域，也是土星极光发射（包括千米辐射）的来源。对于每个区域，我们确定了关键的科学问题，并提出了解决这些问题的调查策略。最后，我们展示了卡西尼号航天器、仪器和任务概况的独特特征如何能够解决并有望解决其中许多问题。虽然卡西尼号轨道之旅可以到达大多数（如果不是全部）需要探索的区域，但 MAPS 仪器套件的独特功能使其能够制定有效的策略，使原位测量和遥感观测相辅相成。在任务的四年中，土星的磁层将得到从微物理到全球范围的广泛研究。这个独特环境中存在的所有相——扩展的固体表面、尘埃和气体云、等离子体和高能粒子——都以复杂的方式耦合在一起，就像它们在行星形成环境中一样。这是土星磁层和等离子体科学研究最有趣的方面之一。它为我们提供了一个独特的机会来对动力系统进行原位研究，该系统在某些方面类似于行星系统形成的尘埃等离子体环境。
Magnetospheric and plasma science studies at Saturn offer a unique opportunity to explore in-depth two types of magnetospheres. These are an ‘induced’ magnetosphere generated by the interaction of Titan with the surrounding plasma flow and Saturn's ‘intrinsic’ magnetosphere, the magnetic cavity Saturn's planetary magnetic field creates inside the solar wind flow. These two objects will be explored using the most advanced and diverse package of instruments for the analysis of plasmas, energetic particles and fields ever flown to a planet. These instruments will make it possible to address and solve a series of key scientific questions concerning the interaction of these two magnetospheres with their environment.The flow of magnetospheric plasma around the obstacle, caused by Titan's atmosphere/ionosphere, produces an elongated cavity and wake, which we call an ‘induced magnetosphere’. The Mach number characteristics of this interaction make it unique in the solar system. We first describe Titan's ionosphere, which is the obstacle to the external plasma flow. We then study Titan's induced magnetosphere, its structure, dynamics and variability, and discuss the possible existence of a small intrinsic magnetic field of Titan.Saturn's magnetosphere, which is dynamically and chemically coupled to all other components of Saturn's environment in addition to Titan, is then described. We start with a summary of the morphology of magnetospheric plasma and fields. Then we discuss what we know of the magnetospheric interactions in each region. Beginning with the innermost regions and moving outwards, we first describe the region of the main rings and their connection to the low-latitude ionosphere. Next the icy satellites, which develop specific magnetospheric interactions, are imbedded in a relatively dense neutral gas cloud which also overlaps the spatial extent of the diffuse E ring. This region constitutes a very interesting case of direct and mutual coupling between dust, neutral gas and plasma populations. Beyond about twelve Saturn radii is the outer magnetosphere, where the dynamics is dominated by its coupling with the solar wind and a large hydrogen torus. It is a region of intense coupling between the magnetosphere and Saturn's upper atmosphere, and the source of Saturn's auroral emissions, including the kilometric radiation. For each of these regions we identify the key scientific questions and propose an investigation strategy to address them.Finally, we show how the unique characteristics of the CASSINI spacecraft, instruments and mission profile make it possible to address, and hopefully solve, many of these questions. While the CASSINI orbital tour gives access to most, if not all, of the regions that need to be explored, the unique capabilities of the MAPS instrument suite make it possible to define an efficient strategy in which in situ measurements and remote sensing observations complement each other.Saturn's magnetosphere will be extensively studied from the microphysical to the global scale over the four years of the mission. All phases present in this unique environment — extended solid surfaces, dust and gas clouds, plasma and energetic particles — are coupled in an intricate way, very much as they are in planetary formation environments. This is one of the most interesting aspects of Magnetospheric and Plasma Science studies at Saturn. It provides us with a unique opportunity to conduct an in situ investigation of a dynamical system that is in some ways analogous to the dusty plasma environments in which planetary systems form.