Collaborative Research: GEM: Propagation and Dissipation of Electromagnetic Ion Cyclotron Waves in the Magnetosphere and Ionosphere

合作研究：GEM：磁层和电离层中电磁离子回旋波的传播和耗散

• 批准号: 2247395
• 负责人: Eun-Hwa Kim
• 金额: $ 55.53万
• 依托单位: Andrews University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2024
• 资助国家: 美国
• 起止时间: 2024-04-01 至 2028-03-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2247395&HistoricalAwards=false
• 关键词: Collaborative; Research; GEM; Propagation; Dissipation

There are many types of plasma waves in the Earth's magnetosphere. For decades it has been observed that ultra-low frequency electromagnetic ion cyclotron (EMIC) waves in the Pc 1-2 frequency range (0.1-5 Hz) near the ion cyclotron frequency are a prominent feature of the magnetosphere-ionosphere system. These waves play an important role in heating ionospheric ions to magnetospheric energies, regulating pressure anisotropy in the magnetosphere, populating the magnetosphere with energetic heavy ions during substorms, and inducing enhanced protons. EMIC waves are known to be excited as left-hand polarized waves near the magnetic equator in the inner magnetosphere and reach the ground propagating along the magnetic field line. Higher-frequency EMIC waves are often filtered during wave propagation to the ground, while lower-frequency EMIC waves can effectively reach the ground. Understanding this phenomenon is complicated because EMIC waves can be affected by various physical processes, the plasma environment along the propagation path in the magnetosphere/ionosphere, and wave properties. The team proposed to understand better the propagation and dissipation of EMIC waves using models and both space and ground-based observations. This collaborative research project consists of scientists from four institutes, including two non-R1 colleges. This project aims to investigate the propagation and dissipation of EMIC waves in the magnetosphere and ionosphere by answering these four scientific questions: 1. How do EMIC waves reach the ground?2. How is EMIC wave propagation affected by geomagnetic activity?3. How does geomagnetic field topology, such as compressed and stretched magnetic field, affect wave propagation?4. What is the significance of EMIC wave polarization in the context of the above parameters and how are wave polarizations related with propagation?The team will employ a state-of-art full-wave simulation code, Petra-M, which uses the finite element method (FEM). One advantage of using the FEM is that various magnetic field topologies and background plasma parameters are easily adopted in the simulation code. The Petra-M code will utilize realistic terrestrial magnetic field topologies (dipole and compressed magnetic field) and density configurations from empirical density models. Wave simulations will be performed to examine wave generation and propagation. The team will also analyze recent observations of these waves by multiple satellites and compare them with the ground magnetometer network observations. To consider the EMIC wave propagation in the inner magnetosphere, the proposers will investigate the following characteristics of the EMIC wave events between space (GOES satellite) and ground, spatial distribution (L and MLT), relationship with solar and geomagnetic activity, the distance between GOES satellites and plasmapause locations, and wave properties such as polarization, frequency, and normal angle. For the EMIC waves in the outer magnetosphere, the team will also investigate space (MMS, THEMIS, and Cluster)-ground conjugate observations using high-latitude ground stations.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

地球磁层中有多种类型的等离子体波。 几十年来，人们观察到离子回旋频率附近的Pc 1-2频率范围（0.1-5 Hz）内的超低频电磁离子回旋（EMIC）波是磁层-电离层系统的一个突出特征。 这些波在将电离层离子加热为磁层能量、调节磁层压力各向异性、在亚暴期间用高能重离子填充磁层以及诱导增强质子方面发挥着重要作用。 众所周知，EMIC 波在内磁层磁赤道附近被激发为左旋极化波，并沿磁场线传播到达地面。 较高频率的EMIC波在波传播到地面的过程中常常被过滤，而较低频率的EMIC波可以有效地到达地面。 理解这种现象很复杂，因为 EMIC 波可能受到各种物理过程、磁层/电离层传播路径上的等离子体环境以及波特性的影响。 该团队建议使用模型以及空间和地面观测更好地了解 EMIC 波的传播和耗散。 该合作研究项目由来自四个研究所的科学家组成，其中包括两个非 R1 学院。本项目旨在通过回答以下四个科学问题来研究EMIC波在磁层和电离层中的传播和耗散：1.EMIC波如何到达地面？2.EMIC波如何到达地面？ EMIC 波的传播如何受地磁活动的影响？3．地磁场拓扑结构（例如压缩磁场和拉伸磁场）如何影响波传播？4．在上述参数的背景下，EMIC 波极化的意义是什么？波极化与传播有何关系？该团队将采用最先进的全波模拟代码 Petra-M，该代码使用有限元方法（有限元法）。 使用 FEM 的优点之一是可以在仿真代码中轻松采用各种磁场拓扑和背景等离子体参数。 Petra-M 代码将利用现实的地球磁场拓扑（偶极子和压缩磁场）和来自经验密度模型的密度配置。 将进行波浪模拟以检查波浪的产生和传播。 该团队还将分析多颗卫星最近对这些波的观测结果，并将其与地面磁力计网络观测结果进行比较。 为了考虑内磁层中的EMIC波传播，提议者将研究空间（GOES卫星）和地面之间的EMIC波事件的以下特征、空间分布（L和MLT）、与太阳和地磁活动的关系、 GOES 卫星和等离子体层顶位置，以及波特性，例如偏振、频率和法线角。 对于外磁层中的 EMIC 波，该团队还将利用高纬度地面站研究空间（MMS、THEMIS 和 Cluster）-地面共轭观测。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准。