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

该项目的目的是通过比较我们的混合模拟代码A.I.K.E.F.的结果来表征土星卫星土卫二的羽流。在第一步中，我们将分析多物种离子中性化学对整体等离子体结构和磁场的影响：不同水基团离子与羽流中水分子反应的速率彼此差异很大。因此，这些离子丰度的变化导致总反应速率的变化，这最终决定了由羽流引起的磁场扰动。因此，需要考虑不同的反应，以合理解释磁场signature.In第二步，我们将把多射流蒙特-卡罗模型的羽流到我们的等离子体模拟，这将包括测量的位置，个别射流以及重力和惯性力。通过比较我们的模拟结果与磁强计数据，我们将描述所有土卫二飞掠的喷流的源强度和可变性。作为第三步，我们将利用混合模型来描述非麦克斯韦速度分布的能力。由于羽流中的拾取，离子形成环形分布，其通过产生离子回旋波而热化。我们将分析环的自洽形成，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.