GEM: Magnetotail Reconnection Signatures at Lunar Orbit

GEM：月球轨道上的磁尾重联特征

• 批准号: 1503097
• 负责人: Andrei Runov
• 金额: $ 29.27万
• 依托单位: University of California-Los Angeles
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-03-01 至 2021-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1503097&HistoricalAwards=false
• 关键词: GEM; Magnetotail; Reconnection; Signatures; Lunar

Earth's magnetic field encloses it in a protective cocoon, called the magnetosphere, deflecting most of the solar wind around it. The solar wind is a stream of charged particles and magnetic fields blowing outward from the Sun, which varies in intensity with solar activity. Because of its interaction with the solar wind, the magnetosphere is compressed on the dayside and extended in a long "magnetotail" on the nightside. The stretched magnetotail field lines store energy extracted from the solar wind. This energy is released by a process called magnetic reconnection, the subject of the present study, during which magnetic energy is converted into plasma flows as well as heating and energization of plasmas within the Earth's magnetosphere. Magnetic reconnection occurs at two locations: one in the near-tail at a distance of 15-30 Earth radii and the other in the distant tail at 100-200 Earth radii. The near-Earth reconnection is explosive, creating high-energy charged particles that are responsible for the dynamic auroras in the upper atmosphere but also for damage to Earth-orbiting satellites. Near-Earth reconnection is largely associated with space weather events called magnetic storms and substorms. In contrast, the distant tail reconnection (about which much less is known) is envisioned to be steadier. It is not understood how the two reconnection sites interact. Of major importance for the present study, fast plasma flows are produced moving both Earthward and tailward from each of these reconnection sites. A satellite at lunar orbit (~60 Earth radii) between the two sites has the important advantage of being able to detect tailward flows from the near-Earth site, and earthward flows from the distant tail site. Thus the connection between the two, and the impact on magnetotail conditions of each, can be investigated from the same mid-tail vantage point. New insights into magnetic reconnection from the suggested study are valuable for research in planetary magnetospheres, as well as astrophysical and laboratory plasmas. The suggested work will provide important training for graduate students. It also includes public outreach and educational activities.To accomplish the goals described above, the proposers will analyze observations from the Artemus (Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon's Interaction with the Sun) satellites in lunar orbit at ~60 Earth radii using case and statistical studies to investigate the occurrence rates of reconnection outflows from both near- and distant-tail reconnection sites, their variations over a range of space weather conditions (quiescent to magnetic storming), the timing between them (i.e., which site activates first), as well as consequences to the mid-tail space environment, such as transient electric field enhancements, changes in the magnetic field geometry, and enhancements in high-energy particle fluxes.

地球磁场将地球包裹在一个保护性的茧中，称为磁层，使大部分太阳风偏转。太阳风是一股从太阳向外吹出的带电粒子和磁场流，其强度随太阳活动而变化。由于它与太阳风的相互作用，磁层在白天被压缩，在夜晚被拉长成一条长长的“磁尾”。延伸的磁尾磁力线储存从太阳风中提取的能量。这种能量是通过一个称为磁重联的过程释放的，这是本研究的主题，在此过程中，磁能转化为等离子体流以及地球磁层内等离子体的加热和冷却。磁场重联发生在两个位置：一个在近尾，距离15-30地球半径，另一个在远尾，距离100-200地球半径。近地重连是爆炸性的，产生了高能带电粒子，这些粒子是高层大气中动态极光的原因，也是对地球轨道卫星造成损害的原因。近地重连主要与称为磁暴和亚暴的空间天气事件有关。相比之下，远尾重联（关于它的了解要少得多）被认为是更复杂的。目前还不清楚这两个重连位点是如何相互作用的。对于本研究来说，最重要的是，快速的等离子体流产生了从这些重连点向地球和向尾部移动。位于两个地点之间的月球轨道（约60个地球半径）上的卫星具有重要优势，能够检测来自近地地点的尾部流和来自遥远尾部地点的向地球流。因此，两者之间的联系，以及对磁尾条件的影响，可以从相同的中尾Vantage位置进行研究。从建议的研究中对磁重联的新见解对于行星磁层以及天体物理和实验室等离子体的研究都很有价值。建议的工作将为研究生提供重要的培训。为了实现上述目标，提议者将分析阿特莫斯号的观测结果，（月球与太阳相互作用的加速、重连、湍流和电动力学）卫星在月球轨道上的约60个地球半径，使用案例和统计研究来调查近尾和远尾重连点的重连流出发生率，它们在一定范围的空间天气条件（静止到磁暴）上的变化，它们之间的定时（即，哪个部位先激活），以及对中尾空间环境的后果，例如瞬态电场增强、磁场几何形状的变化和高能粒子通量的增强。