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首页> 外文期刊>Journal of Geophysical Research, A. Space Physics: JGR >Doppler effects on periodicities in Saturn's magnetosphere
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Doppler effects on periodicities in Saturn's magnetosphere

机译：多普勒效应在土星的周期的研究磁气圈

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摘要

The magnetosphere of Saturn exhibits a wide variety of periodic phenomena in magnetic fields, charged particles, and radio emissions. The periodicities are observed from a moving spacecraft, so an issue arises about the periodicities being influenced by the Doppler effects. Doppler effects can be investigated using models of the periodicities and then flying the spacecraft through the model, effectively measuring any Doppler phenomena with the simulation. Using 200 days of typical elliptical orbits from the Cassini mission at Saturn, three models were tested: an azimuthal wave (or "searchlight") model, a radial wave (or "pond ripple") model, and a model of an outwardly traveling spiral wave. The azimuthal wave model produced virtually no Doppler effects in the periodicities because its wave vector is nearly perpendicular to the spacecraft trajectory. The radial wavemodel generated strong Doppler effects of an upshifted and a downshifted signal (a dual period) on either side of the true period, because the wave vector is either parallel or antiparallel to the spacecraft trajectory. Being intermediate to the searchlight and radial waves, the spiral wave produced Doppler effects but only for low wave speeds (<10 R_S/h). For higher wave speeds the Doppler effects were not as clear. The Doppler effects can be mitigated by employing only observations beyond ~15 R_S where the spacecraft speed is low compared to the wave speed. The observed periodicities over the same 200 day interval do not show evidence of Doppler effects but generally display a single feature at the expected ~10.7h period.
机译：土星磁层展品宽各种各样的磁场周期性现象,带电粒子,和电台的排放。周期的研究从一个移动的观察宇宙飞船,所以会出现一个问题周期的研究由多普勒的影响效果。使用模型的周期的研究,然后飞行宇宙飞船模型,有效测量任何多普勒现象模拟。卡西尼任务在土星轨道,3模型测试:一个方位(或浪潮“探照灯”)模型中,径向波(或“池塘涟漪”)模型,模型的表面上螺旋波旅行。几乎没有产生多普勒效应周期的研究,因为它几乎是波向量垂直于航天器轨迹。径向wavemodel产生强烈的多普勒效应的加速和幅度已经信号(双段)两侧的真正的时期,因为波矢量平行于或反平行的宇宙飞船轨道。中间的探照灯和径向波,但只有螺旋波产生多普勒效应低波速度(< 10 R_S / h)。速度多普勒效应并不明确。可以减轻通过使用多普勒效应只有观察~ 15 R_S之外的宇宙飞船相比,波速度低速度。200天的间隔不显示多普勒的证据但通常显示一个单一特征影响预期的~ 10.7 h。

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