Magnetic portraits of Tethys and Rhea
Magnetic portraits of Tethys and Rhea
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DOI：
10.1016/j.icarus.2007.08.005
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发表时间：
2008-02
期刊：
影响因子：
3.2
通讯作者：
K. Khurana;C. Russell;M. Dougherty
中科院分区：
文献类型：
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作者：
K. Khurana;C. Russell;M. Dougherty
2005年末，卡西尼号飞船分别对土星的两颗冰冷卫星土卫三和土卫五进行了一次飞越。这些飞越的磁场观测提供了这些卫星磁特性的独特肖像。这是第一次观测到这些惰性卫星与土星磁层的亚磁声等离子体的相互作用。由于上游场和等离子体条件非常稳定，我们能够非常详细地观察相互作用。本研究的主要发现之一是，在亚磁声相互作用中，等离子体耗尽区沿磁场方向沿着被大大拉长。基于热离子的场取向速度的考虑，我们表明，重叠的粒子阴影翼形成的惰性月球的下游，使得在每个粒子阴影翼，特定的场取向速度的粒子耗尽。本研究的其他主要发现是：（1）Tethys和Rhea没有任何内部磁场;（2）没有观察到感应产生的场，因为初级感应非常弱（3）土卫三和土卫五对土星磁层没有明显的质量负荷;（4）我们预测将产生波粒子相互作用，从而消除月球/等离子体相互作用产生的相空间空穴。这些波用于使等离子体分布函数各向同性。
The Cassini spacecraft made a single flyby each of Saturn's icy moons Tethys and Rhea in late 2005. The magnetic field observations from these flybys provide unique portraits of the magnetic properties of these moons. These are the first observations of interactions of these inert moons with the sub-magnetosonic plasma of Saturn's magnetosphere. Because the upstream field and plasma conditions are extremely stable, we are able to observe the interaction in great detail. One of the major findings of this study is that the region of plasma depletion is greatly elongated along the field direction in a sub-magnetosonic interaction. Based on the consideration of field aligned velocities of thermal ions, we show that overlapping particle shadow wings form downstream of an inert moon such that in each of the particle shadow wings, particles of specific field aligned velocities are depleted. Other major findings of this study are: (1) Tethys and Rhea are devoid of any internal magnetic field; (2) No induction generated field was observed, as expected because of the extremely weak primary inducing (time varying) field; (3) There is no appreciable mass-loading of Saturn's magnetosphere from Tethys and Rhea; (4) We predict that wave particles interactions would be generated that smooth out the phase space holes created by the moon/plasma interaction. These waves serve to isotropize the plasma distribution function.