Jupiter’s Aurora: Data analysis of Juno/JEDI data and modeling of auroral electron acceleration

木星极光：Juno/JEDI 数据分析和极光电子加速建模

• 批准号: 437450396
• 负责人: Professor Dr. Joachim Saur
• 金额: --
• 依托单位: Applied Physics Laboratory
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/437450396?language=en
• 关键词: Jupiter; Aurora; Data; analysis; Juno

The understanding of Jupiter’s aurora currently experiences a paradigm change due to the new observations by the NASA Juno spacecraft, which is in a polar orbit around Jupiter since July 2016. One of the key discoveries of Juno was that auroral electrons mostly display broad-band energy distributions and are directed towards and away from Jupiter. These types of electron beams are different compared to the pre-Juno expectation of uni-directional mono-energetic beams based on a steady-state electric current system connecting Jupiter’s ionosphere with its magnetosphere. The broadband bi-directional electrons are generally considered to be caused by stochastic acceleration, however our understanding of this stochastic acceleration is currently only at its infancy. Therefore, we propose a combination of data analysis and theoretical modeling for a better understanding of Jupiter’s acceleration processes: (i) We intend to analyze measurements of energetic electrons obtained by the JEDI instrument onboard of Juno to characterize the spatial/temporal structuring of the electron beams and relate them with the theoretically expected structures based on turbulent/stochastic acceleration. (ii) We plan in parallel to theoretically investigate how turbulent Alfvén waves down to kinetic wavelength scales evolve while propagating towards Jupiter’s ionosphere along the strongly increasing magnetic field strength and decreasing plasma density of Jupiter’s magnetosphere. (iii) In these wave fields we then investigate using Monte-Carlo models how electrons are being accelerated and analyse the resulting electron energy distribution functions. We are specifically interested in understanding the effects of a) the strongly evolving waves due to the inhomogeneous magnetospheric properties while propagating towards Jupiter and b) the effects of the turbulent nature of the waves on the resulting electron energy spectra of the beams. (iv) Because electron energies above 300 keV as repeatedly observed by Juno require consideration of the relativistic electron momentum, we also investigate the effects of a fully-relativistic dispersion relationship for Alfvén waves in their kinetic limits.

由于美国宇航局朱诺号航天器的新观测，对木星极光的理解目前经历了一个范式的变化，该航天器自2016年7月以来一直在木星的极地轨道上。朱诺号的关键发现之一是极光电子大多显示宽带能量分布，并且朝向和远离木星。这些类型的电子束与朱诺号之前基于连接木星电离层与磁层的稳态电流系统的单向单能量束的预期不同。宽带双向电子通常被认为是由随机加速引起的，然而我们对这种随机加速的理解目前还处于起步阶段。因此，我们提出了数据分析和理论建模相结合，以更好地了解木星的加速过程：（i） 我们打算分析由朱诺号上的JEDI仪器获得的高能电子的测量结果，以表征电子束的空间/时间结构，并将它们与基于湍流/随机加速的理论预期结构联系起来。 (ii)我们计划在平行的理论研究如何湍流阿尔文波的动力学波长尺度的演变，同时向木星的电离层沿着强烈增加的磁场强度和木星的磁层的等离子体密度下降。 (iii)在这些波场中，我们然后调查使用蒙特-卡罗模型如何电子被加速，并分析由此产生的电子能量分布函数。 我们特别感兴趣的是理解的影响a）强烈演变的波，由于不均匀的磁层属性，而向木星和B）的影响的湍流性质的波上产生的电子能谱的光束。(iv)由于电子能量超过300千电子伏的朱诺号反复观察需要考虑相对论电子动量，我们还调查了一个完全相对论色散关系的阿尔文波在其动力学极限的影响。