Acceleration of Electrons in a Reconnecting Magnetotail

GSTDTAP

项目编号	1450864
	Acceleration of Electrons in a Reconnecting Magnetotail
	Maha Ashour-Abdalla
主持机构	University of California-Los Angeles
项目开始年	2015
	2015-09-15
项目结束日期	2018-08-31
资助机构	US-NSF
项目类别	Continuing grant
项目经费	122829(USD)
国家	美国
语种	英语
英文摘要	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.
来源学科分类	Geosciences - Atmospheric and Geospace Sciences
文献类型	项目
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/68818
专题	环境与发展全球科技态势
推荐引用方式 GB/T 7714	Maha Ashour-Abdalla.Acceleration of Electrons in a Reconnecting Magnetotail.2015.