Acceleration of Electrons in a Reconnecting Magnetotail

近地空间环境的动态是由太阳风和地球磁场之间的相互作用驱动的。 地球夜面的一个特征是磁场中能量的循环储存和爆炸性释放。 关于磁能如何转化为加热以及在这个过程中等离子体的大规模传输的详细理解仍然困扰着我们。 一个悬而未决的问题是电子加速到很高的能量。 观测表明，这种现象发生的规模比所涉及的小规模物理过程容易解释的要大得多。 最近的研究证实，在这些事件中，夜面区域的大规模动力学是太阳黑子的主要来源。 纠缠的过程在广泛的尺度范围内的一个全面的，定量的描述高能电子的产生和演化的复杂组合是磁层物理学的一个重要的当前挑战。 该项目将利用先进的计算机代码来模拟所涉及的小规模和大规模过程对粒子的影响。将对航天器观测到的三个真实事件的模拟结果进行分析和比较，以确定电子在这些事件中的加速位置和方式。 该团队将采用新颖的多尺度方法，承诺提供对各种过程的相对作用的第一次定量评估。 它还将为跨尺度耦合的重要性提供至关重要的新见解。 作为本研究主题的磁能转换过程是一种通用的等离子体物理过程，可在广泛的空间和实验室等离子体中运行。地球的磁层是研究这种过程的天然实验室，在那里可以进行模拟和直接观测。因此，该项目的结果将影响广泛的研究领域。 当具有巨大能量的电子被推回地球时，它们会影响近地空间环境。 其中一些被困在那里更强的磁场中，并有助于构成地球辐射带。 另一些则沉淀到高层大气中，在那里的影响有助于创造，除其他外，强烈的极光显示。 近地空间环境中的扰动效应令可能受到影响的卫星和地球表面其他技术系统感到关切。 这为研究增加了广泛的社会相关性和重要性。 该项目将通过培训一名研究生，将研究和教育结合起来。研究生将与团队成员合作，以补充他的论文工作的多尺度过程。此外，一些本科实习生将在夏季参加该项目。 最后，PI是国际空间模拟学校（ISSS）项目委员会的创始人和成员。这所学校专注于学生学习模拟技术。作为本项目的一部分，PI将继续积极参与该活动。这是一个以磁尾为重点的数值模拟项目。 其目标是确定在磁层亚暴期间电子在何处以及如何加速。目的是了解加速过程的多尺度性质，包括中性线附近发生的动力学过程的影响，同时考虑到磁尾结构的全球变化。特别是，这项研究将量化的相对作用的重联和双极化前沿在激发电子在亚暴事件。 以前的研究与双极化前沿的电子加速已经进行了使用本地粒子在细胞（PIC）模拟或大规模的动力学计算的基础上，以下大量的电子在时间依赖性的电场和磁场从全球磁流体动力学（MHD）模拟。在这里，将采用多尺度方法，结合动力学过程的影响，包括中性线附近发生的波粒相互作用，同时考虑到磁尾配置的全球变化。通过将边界处的磁场和粒子流设置为MHD结果给出的值，将使用全局MHD模拟的结果来确定三维粒子模拟的初始和边界条件。模拟系统将包括从重连点发出的快速流出区域，该区域驱动偶极前沿的形成。在隐式粒子在细胞代码（iPIC3d）中看到的加速将被表征，以解决重连位点附近的电子自旋的问题。最后，大规模的动力学模拟，使用的电场和磁场的MHD模拟将提供信息的降水和降水损失的偶极锋向地球移动。绝热和非绝热加热的电子的影响将比较和对比几个模拟之间，以确定是否占主导地位的加速和加热机制是不同的各种亚暴，是什么原因造成的变化。

The dynamics of the space environment near Earth is driven by the interaction between the solar wind and the Earth's magnetic field. A characteristic feature on the nightside of Earth is a cyclic storage and explosive release of energy in the magnetic field. The detailed understanding of how magnetic energy is converted into heating and large-scale transport of the plasma in this process still eludes us. One outstanding question concerns the acceleration of electrons to very high energies. Observations show that this happens on a much larger scale than can easily be explained by the small-scale physical processes involved. Recent studies have confirmed the large-scale dynamics of the nightside region during these events as the dominant source for the energization. Entangling the complex mix of processes over a wide range of scales for a comprehensive, quantitative description of the generation and evolution of the energetic electrons is an important current challenge in magnetospheric physics. This project will utilize a combination of advanced computer codes to simulate the effects on the particles of both the small- and large-scale processes involved. Simulation results from three real-life events observed by spacecraft will be analyzed and compared to determine where and how electrons are accelerated during these events. The novel multi-scale approach the team will employ promises to provide the first quantitative assessment of the relative roles of the various processes. It will also provide crucial new insights into the importance of cross-scale coupling. The magnetic energy conversion process that is the subject of this study is a generic plasma physics process that operates in a wide range of space and laboratory plasmas. The Earth's magnetosphere is a natural laboratory for studying such processes, where both simulations and direct observations are possible. Results from this project therefore will impact a broad variety of research areas. When the electrons with great energy are propelled back toward Earth, they can impact the near-Earth space environment. Some are trapped in the stronger magnetic field there and contribute to the make-up of the Earth radiation belts. Others precipitate into the upper atmosphere where the impact contributes to the creation, amongst others, of strong auroral displays. The disturbance effects in the space environment near Earth are of concern for satellites and other technological systems on the Earth surface that might be affected. This adds broad societal relevance and importance to the research study. The project will integrate research and education through the training of a graduate student. The graduate student will work with members of the team to complement his thesis work on multi-scale processes. In addition, a number of undergraduate interns will participate in the project during the summers. Finally, the PI is a founder and member of the program committee for the International School for Space Simulations (ISSS). This school focuses on student learning of simulation techniques. The PI will continue her active involvement with this activity as part of this project. This is a numerical modeling project focused on the magnetotail. Its goal is to determine where and how electrons are accelerated during magnetospheric substorms. The aim is to understand the multi-scale nature of the acceleration process by including the effects of kinetic processes that occur near the neutral line while taking into account the global changes in the configuration of the magnetotail. In particular, the study will quantify the relative role of reconnection and dipolarization fronts in energizing electrons during substorm events. Previous investigations of the acceleration of electrons associated with dipolarization fronts have been carried out using either local particle-in-cell (PIC) simulations or large-scale kinetic calculations based on following large numbers of electrons in the time dependent electric and magnetic fields obtained from global Magneto-Hydro-Dynamic (MHD) simulations. Here, a multi-scale approach will be adopted that incorporates the effects of kinetic processes, including wave-particle interactions that occur near the neutral line, while taking into account the global changes in the configuration of the magnetotail. The results of global MHD simulations will be used to determine the initial and boundary conditions of a three-dimensional particle in cell simulation by setting the magnetic fields and particle flows at the boundaries to the values given by the MHD results. The simulation system will include the region of fast outflow emanating from the reconnection site that drives the formation of dipolarization fronts. The acceleration seen in the implicit-particle-in-cell code (iPIC3d) will be characterized in order to address the questions of electron energization near the reconnection site. Finally, large-scale kinetic simulations using the electric and magnetic fields from the MHD simulation will provide information on energization and precipitation loss as the dipolarization front moves earthward. The effects of adiabatic and non-adiabatic heating of the electrons will be compared and contrasted between several simulations to determine whether the predominant acceleration and heating mechanisms are different for various substorms and what causes that variation.