GEM: Construction of a Storm-Time Plasma Sheet Model Including Effects of Bubble Injections

从外磁层向地球的等离子体传输被认为是由大规模对流主导的。然而，卫星观测给出了一种新的观点，即通过磁层的等离子体质量和能量向地球的传输估计有60%-100%是以流爆发(速度超过400Km/S的短暂流)和爆发体流(包含流爆发的持续时间较长的流)的形式进行的。这些爆发的块状流(BBF)与等离子体片气泡(闭合磁通量区域，比其周围的熵更低)有关。较低的熵使它们更容易被注入到内部磁层，因此，它们所包含的粒子可能是环电流和辐射带的重要种子和源种群。这种具有气泡结构和向地球流动爆发的等离子体片的发展观点与通常使用的等离子体片模型中相对平滑的等离子体分布和大范围流动有很大的不同。该项目的目标是建立第一个经验等离子体片模型，其中明确包括地磁风暴期间气泡/BBF注入的气候学。新模型将免费提供，从而成为从事磁层研究的其他团体的宝贵资源。在一系列模拟中使用这一新模型，研究小组将解决一些问题，这些问题旨在加强对气泡在为内磁层高能辐射提供源种群方面的影响的理解。该项目将为职业早期研究人员的专业发展提供支持，为研究生提供培训，为高中生提供研究经验，从而为建设未来的科学队伍做出贡献。这些提出者采用了一种有趣的方法来构建等离子体片模型。研究小组将不再使用观测数据来建立经验模型，而是使用系统的数据约束计算机模拟来获得近地等离子体片中等离子体和电场分布的统计特征。模拟将进行优化，以匹配观测到的地磁指数、气泡/BBF的统计特性和背景等离子体分布。新建立的模型将包含关于背景分布和中尺度间歇气泡注入的全部统计信息。提案团队将使用该模型来探索：(1)气泡/BBF注入如何在地磁风暴的不同阶段调制近地等离子体片中等离子体和电场的背景分布，以及(2)如何通过气泡/BBF注入将辐射带电子的种子和源群体传输到地球同步轨道并沿地球同步轨道分布。

Plasma transport from the outer magnetosphere towards the Earth was thought to be dominated by large-scale convective flows. However, satellite observations have given a new view in which an estimated 60%-100% of the Earthward transport of plasma mass and energy through the magnetosphere is in the form of flow bursts (short-lived flows with velocities exceeding 400 km/s) and bursty bulk flows (longer duration flows containing flow bursts). These bursty bulk flows (BBFs) are associated with plasma-sheet bubbles (regions of closed magnetic flux with lower entropy than their surroundings). The lower entropy makes it possible for them to be more easily injected into the inner magnetosphere and thus, the particles they contain may be important seed and source populations for the ring current and radiation belts. This developing view of the plasma sheet with bubble structures and bursts of Earthward flow is far different than the relatively smooth plasma distributions and large-scale flows in plasma sheet models that are in common usage. The goal of this project is to construct the first empirical plasma-sheet model that explicitly includes the climatology of bubble/BBF injections during geomagnetic storms. The new model will be made freely available and thus serve as a valuable resource for other groups engaged in magnetospheric research. Using this new model in a series of simulations, the research team will address questions that are aimed at enhancing understanding about the effects of the bubbles in providing a source population for the high-energy radiation in the inner magnetosphere. The project will provide support for the professional development of an early-career researcher, training for graduate students, and a research experience for high school students, thus contributing to building the future scientific workforce. The proposers take an interesting approach to the construction of the plasma sheet model. Instead of using observations to build an empirical model, the research team will obtain the statistical features of the plasma and electric field distributions in the near-Earth plasma sheet using systematic data-constrained computer simulations. The simulations will be optimized to match observed geomagnetic indices, statistical properties of bubbles/BBFs and the background plasma distribution. The newly constructed model will contain the full statistical information on both the background distribution and the meso-scale intermittent bubble injections. The proposal team will use the model to explore: (1) how bubble/BBF injections modulate the background distribution of plasma and electric field in the near-Earth plasma sheet during different phases of geomagnetic storms, and (2) how the seed and source populations for the radiation belt electrons are transported to and distributed along geosynchronous orbit through bubble/BBF injections.