Modelling of the ring current in Saturn's magnetosphere
Modelling of the ring current in Saturn's magnetosphere
复制标题
土星磁层环电流的建模
DOI：
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
M. Dougherty
中科院分区：
文献类型：
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作者：
G. Giampieri;M. Dougherty
抽象的。土星磁层内存在环电流的说法首先是由史密斯等人提出的。(1980)和Ness et al.(1981,1982)，以解释先锋11号和旅行者1号和2号航天器在磁场观测中的各种特征。Connerney等人。(1983)在以前对木星电流片的建模工作的基础上，形式化了赤道流模型，并从两个Voyager数据集估计了它的参数。在这里，我们通过重新考虑来自两个旅行者号航天器的数据，以及包括先锋11号飞越数据集，进一步研究该模型。首先，我们得到了闭合形式的环电流产生的磁场的解析表达式。然后，考虑到所有可用的数据，我们将模型拟合到外场，即观察场和内部磁场之间的差值。总体而言，与以前的模型相比，通过我们的全局拟合可以获得更准确的参数。我们指出了三次飞行的模型参数之间的差异，并研究了与模型中假定的轴对称和平面对称可能存在的偏差。我们的结论是，对土星圆盘电流的准确模拟需要考虑到与磁层条件有关的时间变化以及由于当地时间效应而产生的非轴对称贡献。关键词。磁层物理学(电流系统；行星磁层；等离子体片)
Abstract. The existence of a ring current inside Saturn's magnetosphere was first suggested by Smith et al. (1980) and Ness et al. (1981, 1982), in order to explain various features in the magnetic field observations from the Pioneer 11 and Voyager 1 and 2 spacecraft. Connerney et al. (1983) formalized the equatorial current model, based on previous modelling work of Jupiter's current sheet and estimated its parameters from the two Voyager data sets. Here, we investigate the model further, by reconsidering the data from the two Voyager spacecraft, as well as including the Pioneer 11 flyby data set. First, we obtain, in closed form, an analytic expression for the magnetic field produced by the ring current. We then fit the model to the external field, that is the difference between the observed field and the internal magnetic field, considering all the available data. In general, through our global fit we obtain more accurate parameters, compared to previous models. We point out differences between the model's parameters for the three flybys, and also investigate possible deviations from the axial and planar symmetries assumed in the model. We conclude that an accurate modelling of the Saturnian disk current will require taking into account both of the temporal variations related to the condition of the magnetosphere, as well as non-axisymmetric contributions due to local time effects. Key words. Magnetospheric physics (current systems; planetary magnetospheres; plasma sheet)