GEM: Cold Dense and/or Heavy Plasma Controlling the Magnetopause Dynamics

GEM：控制磁层顶动力学的冷致密和/或重等离子体

• 批准号: 1834451
• 负责人: Kyoung-Joo Hwang
• 金额: $ 31.98万
• 依托单位: Southwest Research Institute
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-09-01 至 2021-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1834451&HistoricalAwards=false
• 关键词: GEM; Cold; Dense; Heavy; Plasma

The effects of oxygen ions, flowing out of the ionosphere, on the processes that allow mass, energy, and momentum from the solar wind to penetrate into the magnetosphere is an open question of critical importance in understanding the way the Geospace system works to protect the Earth. This is also a critical element affecting how space weather disturbances are generated in our vicinity. The Geospace system is composed of: (1) the upper regions of our atmosphere, (2) the ionosphere (which is an embedded layer of ions within this region), and (3) the magnetosphere (which is the extension of the Earth's magnetic field into space). The solar wind is the hot upper atmosphere of the sun, which gravity is unable to contain, blowing outward carrying with it solar magnetic fields. Only a few percent of the energy in the solar wind actually leaks into the magnetosphere, which acts as a magnetic shield, but this is enough to power severe space weather disturbances near the Earth. One way solar wind mass and energy leaks into the magnetosphere is through magnetic reconnection which is, essentially, the breaking of the Earth's magnetic field lines and joining with the interplanetary magnetic field lines, accompanied by explosive energy releases. In another process, solar wind momentum and mass are transmitted across the magnetopause through large vortices (called Kelvin-Helmholtz waves) that develop at the interface between the fast solar wind and the much slower magnetospheric plasma. However during disturbed space weather conditions, heated ionospheric oxygen ions flow outward and mix with the hotter more tenuous hydrogen ions in the dayside magnetosphere. Their presence alters the conditions for magnetic reconnection and for the formation of Kelvin-Helmholtz waves. This modulates the entry of the solar wind in unknown ways. This project will combine a coordinated set of spacecraft and ground-based observations with global models to investigate how these processes change in the presence of cooler denser ionospheric-origin oxygen ions and what controls the amount of these oxygen ions that reach the magnetosphere. New knowledge about how the Geospace system works is expected to result from this investigation. The broader impacts are significant including: the further training of a postdoctoral researcher who is also a co-I on the project, the support of two female scientists (one being the PI), which contributes to diversity in the field, and a plan for participating in outreach activities involving high school and undergraduate students. Knowledge gained from this work will also be of interest to researchers studying solar system, astrophysical and laboratory plasmas and will in the long-term be an important component in improving the ability to forecast space weather disturbances of importance to society.The methodology of the study will combine both statistical and case studies of coordinated observations that connect the dayside magnetopause with outflows from the upper ionosphere or plasmaspheric drainage plumes from the inner magnetosphere. The coordinated observations of magnetosphere and ionosphere parameters will be taken from the MMS, THEMIS, Cluster, Van Allen Probes, DMSP, and FAST satellite datasets; solar wind parameters from ACE and Wind satellites upstream of the Earth; and information on the magnetopause/magnetosphere from ground-based observations including magnetograms, radar and all-sky imagers. Simulations of the global magnetosphere will be used to aid in interpreting the observations.

从电离层流出的氧离子对太阳风的质量、能量和动量进入磁层的过程的影响是一个悬而未决的问题，对于理解地球空间系统保护地球的方式至关重要。这也是影响我们附近空间天气干扰如何产生的关键因素。地球空间系统由：(1)我们大气层的上层区域，(2)电离层（电离层是该区域内的离子嵌入层）和(3)磁层（是地球磁场向太空的延伸）组成。太阳风是太阳上层的热大气，重力无法控制它，它向外吹，携带着太阳磁场。太阳风中只有百分之几的能量会泄漏到磁层中，磁层起着磁屏蔽的作用，但这足以给地球附近的太空天气造成严重干扰。太阳风质量和能量泄漏到磁层的一种方式是通过磁重联，本质上是地球磁力线的断裂，并与行星际磁力线结合，伴随着爆炸性的能量释放。在另一个过程中，太阳风的动量和质量通过在快速太阳风和慢得多的磁层等离子体之间的界面上形成的大漩涡（称为开尔文-亥姆霍兹波）在磁层顶传递。然而，在受到干扰的太空天气条件下，被加热的电离层氧离子向外流动，并与白天磁层中更热、更脆弱的氢离子混合。它们的存在改变了磁重联和开尔文-亥姆霍兹波形成的条件。这以未知的方式调节了太阳风的进入。该项目将结合一组协调的航天器和地面观测与全球模型，研究这些过程在电离层起源的更冷、密度更大的氧离子存在下是如何变化的，以及是什么控制了这些氧离子到达磁层的数量。关于地球空间系统如何工作的新知识有望从这次调查中得到。更广泛的影响是显著的，包括：进一步培训一名博士后研究员，她也是该项目的共同i，两名女科学家（其中一名是PI）的支持，这有助于该领域的多样性，以及参与涉及高中和本科生的外展活动的计划。从这项工作中获得的知识也将对研究太阳系、天体物理学和实验室等离子体的研究人员感兴趣，并将在长期内成为提高预测对社会重要的空间天气干扰能力的重要组成部分。该研究的方法将结合统计和协调观测的案例研究，这些观测将白天磁层顶与上层电离层的流出物或内部磁层的等离子层排水羽流联系起来。磁层和电离层参数的协调观测将采用MMS、THEMIS、Cluster、Van Allen探测器、DMSP和FAST卫星数据集；来自地球上游ACE和wind卫星的太阳风参数；以及来自地面观测的磁层顶/磁层的信息，包括磁图、雷达和全天成像仪。对全球磁层的模拟将用于帮助解释观测结果。