Quantifying Energetic Electron Precipitation Driven By Magnetospheric Waves

量化磁层波驱动的高能电子沉淀

• 批准号: 1564510
• 负责人: Wen Li
• 金额: $ 51.15万
• 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: 2016-05-01 至 2017-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1564510&HistoricalAwards=false
• 关键词: Quantifying; Energetic; Electron; Precipitation; Driven

Waves exist in space plasmas just as in the oceans and the atmosphere. In these plasmas, collisions between charged particles are rare. As a result, plasma waves are a major means of transferring energy from one charged particle population to another. Charged particles "surf" the waves. To first order, those that are moving slightly faster than the waves are energized, while those moving slower lose energy to the waves causing them to grow. There are a wide variety of plasma waves with different properties and different source mechanisms. Three of these (plasmaspheric hiss, chorus, and electromagnetic ion cyclotron (EMIC) waves) are widely believed to play significant roles in the depletion of the electron radiation belts but how this happens and how each contributes with local time and radial distance are still-open and strongly debated questions of fundamental importance. During their interactions with the waves, electrons are scattered out of their trapped orbits and sent on trajectories into the dense atmosphere where they are lost through collisions. The work will independently examine experimental observations and, most importantly, use theoretical tools to understand the interactions leading to the precipitation. The science questions to be addressed in this proposal are particularly important, since electron precipitation leads to chemical changes in the upper atmosphere, and is critical in regulating ring current and radiation belt electron dynamics. The grant will support the further training and development of a promising female early-career scientist. The results will be useful to the broader space physics and upper atmosphere communities, to researchers studying the chemistry of the middle atmosphere, and for space environment applications, such as active mitigation techniques for both natural and artificial radiation in space.Testing theoretical ideas about particular wave-particle interactions and the variations in the space environment that effect them has been difficult because the waves are measured at large radial distances in the magnetosphere while the electron precipitation that they produce must be viewed from low-earth orbit. To complicate matters, the mix of plasma waves depends on the radial distance and magnetic local time but in addition is an as yet to be determined function of the severity of space weather storming, and the phase of the storm. The principal investigator (PI) has developed an innovative technique to analyze the physical relationship between wave intensity and wave-driven electron pitch angle scattering loss, which can be directly implemented using conjugate observations from near-equatorial and low-altitude satellites. This project, which uses both theory and observation, will provide a definitive understanding of the quantitative contribution of each type of plasma wave to electron precipitation within various energy ranges and in different L-MLT regions. The results will provide a highly important contribution to our wider understanding of the mechanisms that regulate the hazardous radiation environment surrounding the Earth.

波存在于空间等离子体中，就像在海洋和大气中一样。在这些等离子体中，带电粒子之间的碰撞很少。因此，等离子体波是将能量从一个带电粒子群转移到另一个带电粒子群的主要手段。带电粒子在波浪中"冲浪"。对于第一阶，那些运动速度略快于波的物体被激发，而那些运动速度较慢的物体则将能量输给波，从而使它们生长。等离子体波种类繁多，具有不同的性质和不同的源机制。其中三个（等离子体层嘶嘶声，合唱和电磁离子回旋（EMIC）波）被广泛认为在电子辐射带的耗尽中发挥了重要作用，但这是如何发生的，以及每个如何与当地时间和径向距离的贡献仍然是开放的和激烈争论的问题。在它们与波的相互作用过程中，电子被散射出它们被困的轨道，并沿着轨道进入稠密的大气层，在那里它们通过碰撞而丢失。这项工作将独立检查实验观察，最重要的是，使用理论工具来理解导致降水的相互作用。这项建议中要解决的科学问题特别重要，因为电子沉淀导致高层大气的化学变化，对调节环电流和辐射带电子动力学至关重要。这笔赠款将支持一名有前途的女性早期职业科学家的进一步培训和发展。这些结果将有助于更广泛的空间物理学和高层大气界、研究中层大气化学的研究人员以及空间环境应用，如太空中天然和人工辐射的主动减缓技术。测试有关特定波的理论想法-粒子相互作用和影响它们的空间环境变化一直很困难，因为波是在大的径向距离上测量的。它们产生的电子沉淀必须从低地球轨道观察。更复杂的是，等离子体波的混合取决于径向距离和磁性当地时间，但除此之外，还取决于空间天气风暴的严重程度和风暴的阶段。首席研究员（PI）开发了一种创新技术来分析波强度和波驱动电子俯仰角散射损失之间的物理关系，可以直接使用近赤道和低空卫星的共轭观测来实现。这个项目，它使用的理论和观察，将提供一个明确的理解的定量贡献的每种类型的等离子体波的电子沉淀在不同的能量范围内，并在不同的L-MLT区域。研究结果将为我们更广泛地了解地球周围有害辐射环境的调节机制作出非常重要的贡献。