Quantitative characterization of Enceladus' plume and its variability using hybrid simulations and Cassini magnetometer data

这个项目的目的是通过比较我们的混合模拟代码A.I.K.E.F.（自适应离子动力学电子流体）的结果与卡西尼号宇宙飞船的观测结果来表征土星卫星土卫二的羽流。在第一步中，我们将分析多组分离子中性化学对等离子体整体结构和磁场的影响：羽流中不同的水基团离子与水分子的反应速率彼此之间存在很大差异。因此，这些离子丰度的变化导致了总反应速率的变化，这最终决定了羽流引起的磁场扰动。因此，为了合理地解释磁场特征，需要考虑不同的反应。在第二步中，我们将把羽流的多喷流蒙特卡罗模型纳入我们的等离子体模拟，其中将包括单个喷流的测量位置以及引力和惯量力。通过将我们的模拟结果与磁力计数据进行比较，我们将描述土卫二所有飞掠的源强度和射流的变化。作为第三步，我们将利用混合模型的能力来描述非麦克斯韦速度分布。由于羽流中的吸收，离子形成环状分布，通过产生离子回旋波而热化。我们将分析环的自一致性形成，并将相关波与MAG数据相关联，以便进一步了解土卫二的拾取过程。

The purpose of this project is to characterize the plume of Saturn’s moon Enceladus by comparing results from our hybrid simulation code A.I.K.E.F. (adaptive ion kinetic electron fluid) with observations made by the Cassini spacecraft.In a first step, we will analyze the influence of multi-species ion-neutral chemistry on the overall plasma structures and magnetic field: The rates for the reactions of the different water group ions with the water molecules in the plume strongly differ from each other. The resulting changes in the abundances of these ions therefore cause variations of the total reaction rate, which finally determines the magnetic field perturbation caused by the plume. Thus, the different reactions need to be considered for a reasonable interpretation of magnetic field signatures.In a second step, we will incorporate a multi-jet Monte-Carlo model of the plume into our plasma simulation, which will include the measured locations of individual jets as well as gravitational and inertia forces. By comparing the results of our simulations with magnetometer data, we are going to characterize the source strength and variability of the jets for all Enceladus flybys.As a third step, we will exploit the capablity of hybrid models to describe non-Maxwellian velocity distributions. Due to pick-up in the plume, the ions form a ring distribution, which thermalizes by generating ion-cyclotron waves. We will analyze the self-consistent formation of the ring and correlate the associated waves with MAG data in order to provide further insight into the pick-up process at Enceladus.