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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >On Euronpa's magnetospheric interaction: A MHD simulation of the E4 flyby
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On Euronpa's magnetospheric interaction: A MHD simulation of the E4 flyby

机译:关于Euronpa的磁层相互作用:E4飞越的MHD模拟

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The global three-dimensional interaction of Europa with the Jovian magnetosphere is modeled by using a complete set of ideal magnetohydrodynamic (MHD) equations. The model accounts for exospheric mass loading, ion-neutral charge exchange, recombination, and a possible intrinsic dipole magnetic field of Europa. The single-fluid MHD equations are solved by using a modern, finite volume, higher-order, Godunov-type method on an adaptively refined unstructured grid, which allows detailed modeling of the region near Europa while still resolving both the upstream region and the satellite's wake. The magnetic field and plasma density measured during Galileo's E4 flyby of December 19, 1996, are reproduced reasonably well in the simulation. We find the agreement between the data and our model particularly convincing if we assume that the plasma velocity during the E4 flyby deviated from the nominal corotation direction by approximately 20 deg. Evidence from the Galileo energetic particle detector also supports this assumption. In this case, we can fit the data using a dipole with orientation close to that of an induced dipole arising from the interaction of a hypothetical conducting subsurface layer on Europa with the periodically changing magnetic field of Jupiter. However, the magnitude of the dipole in our model is somewhat smaller (70%) than that suggested by Khurana et al. [1998]. The total mass loading and ion-neutral charge exchange rates are consistent with the estimates of Europa's atmosphere and ionosphere.
机译:欧罗巴与木星磁层的全球三维相互作用是通过使用一组完整的理想磁流体动力学(MHD)方程建模的。该模型说明了大气层的质量负载,离子中性电荷交换,复合以及欧罗巴可能的本征偶极子磁场。通过在自适应细化的非结构化网格上使用现代的有限体积,高阶,Godunov型方法来求解单流体MHD方程,该方法可以对Europa附近的区域进行详细建模,同时仍可以解析上游区域和卫星的唤醒。在模拟中可以很好地再现1996年12月19日伽利略号E4飞越期间测得的磁场和等离子体密度。如果我们假设E4飞越期间的等离子体速度偏离名义同向旋转大约20度,我们会发现数据与模型之间的一致性特别令人信服。来自伽利略高能粒子探测器的证据也支持这一假设。在这种情况下,我们可以使用偶极子对数据进行拟合,该偶极子的方向接近感应偶极子的方向,该方向是由木卫二上的假设导电地下层与木星的周期性变化磁场相互作用而产生的。但是,我们模型中偶极子的大小比Khurana等人建议的小(70%)。 [1998]。总的质量负载和离子中性电荷交换速率与欧罗巴大气层和电离层的估计值一致。

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