Europa hosts a periodically changing plasma interaction driven by the variations of Jupiter's magnetic field and magnetospheric plasma. We have developed a multi‐fluid magnetohydrodynamic (MHD) model for Europa to characterize the global configuration of the plasma interaction with the moon and its tenuous atmosphere. The model solves the multi‐fluid MHD equations for electrons and three ion fluids (Jupiter's magnetospheric O⁺, as well as O⁺ and O₂⁺ originating from Europa's atmosphere) while incorporating sources and losses in the MHD equations due to electron impact and photo‐ionization, charge exchange, recombination and other relevant collisional effects. Using input parameters constrained by the Galileo magnetic field and plasma observations, we first demonstrate the accuracy of our model by simulating the Galileo E4 and E14 flybys, which took place under different upstream conditions and sampled different regions of Europa's interaction. Our model produces 3D magnetic field and plasma bulk parameters that agree with and provide context for the flyby observations. We next present the results of a parameter study of Europa's plasma interaction at three different excursions from Jupiter's central plasma sheet, for three different global magnetospheric states, comprising nine steady‐state simulations. By separately tracking multiple ion fluids, our MHD model allows us to quantify the access of the Jovian magnetospheric plasma to Europa's surface and determine how that access is affected by changing magnetospheric conditions. We find that the thermal magnetospheric O⁺ precipitation rate ranges from (1.8–26) × 10²⁴ ions/s, and that the precipitation rate increases with the density of the ambient magnetospheric plasma.

中文翻译：

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不同磁层条件下欧罗巴等离子体相互作用的多流体MHD模拟

木星的磁场和磁层等离子体的变化驱动欧罗巴定期改变等离子体相互作用。我们为欧罗巴开发了一种多流体磁流体动力学（MHD）模型，以表征与月球及其微弱大气的等离子体相互作用的整体结构。该模型解决了电子和三种离子流体（木星的磁层O ⁺以及O ⁺和O ₂ ⁺源自欧罗巴的大气），同时将由于电子撞击和光电离，电荷交换，复合和其他相关碰撞效应而在MHD方程中纳入了源和损失。使用受伽利略磁场和等离子体观测值约束的输入参数，我们首先通过模拟伽利略E4和E14飞越（在不同的上游条件下进行并采样欧罗巴相互作用的不同区域）来证明模型的准确性。我们的模型会产生3D磁场和等离子体参数，这些参数与飞越观测相符并为其提供背景信息。接下来，我们将针对三种不同的全球磁层状态，在来自木星中央等离子体片的三种不同偏移中，对欧罗巴等离子体相互作用进行参数研究的结果，包括九个稳态仿真。通过分别跟踪多种离子流体，我们的MHD模型使我们能够量化木星电磁层等离子体对木卫二表面的访问，并确定磁层条件变化对访问的影响。我们发现热磁层O⁺沉淀速率范围为（1.8–26）×10 ²⁴离子/ s，并且沉淀速率随周围磁层等离子体的密度而增加。